|Creator||Ramkhamhaeng the Great|
Thai, Southern Thai
Pattani Malay and others
|ISO 15924||Thai, 352 , Thai|
|The Brahmic script and its descendants|
The Thai script (Thai: , RTGS: akson thai) is the abugida used to write Thai, Southern Thai and many other languages spoken in Thailand. The Thai alphabet itself (as used to write Thai) has 44 consonant symbols (Thai: ?, phayanchana), 16 vowel symbols (Thai: , sara) that combine into at least 32 vowel forms and four tone diacritics (Thai: or ?, wannayuk or wannayut) to create characters mostly representing syllables.
Although commonly referred to as the "Thai alphabet", the script is in fact not a true alphabet but an abugida, a writing system in which the full characters represent consonants with diacritical marks for vowels; the absence of a vowel diacritic gives an implied 'a' or 'o'. Consonants are written horizontally from left to right, and vowels following a consonant in speech are written above, below, to the left or to the right of it, or a combination of those.
The Thai alphabet is derived from the Old Khmer script (Thai: , akson khom), which is a southern Brahmic style of writing derived from the south Indian Pallava alphabet (Thai: ). According to tradition it was created in 1283 by King Ramkhamhaeng the Great (Thai: ). The earliest attestation of the Thai script is the Ram Khamhaeng Inscription dated to 1292, however some scholars question its authenticity. The script was derived from a cursive form of the Old Khmer script of the time. It modified and simplified some of the Old Khmer letters and introduced some new ones to accommodate Thai phonology. It also introduced tone marks. Thai is considered to be the first script in the world that invented tone markers to indicate distinctive tones,which are lacking in the Mon-Khmer (Austroasiatic languages) and Indo-Aryan languages from which its script is derived. Although Chinese and other Sino-Tibetan languages have distinctive tones in their phonological system, no tone marker is found in their orthographies. Thus, tone markers are an innovation in the Thai language that later influenced other related Tai languages and some Tibeto-Burman languages on the Southeast Asian mainland. Another addition were consonant clusters that were written horizontally and contiguously, rather than writing the second consonant below the first one. Finally, the script wrote vowel marks on the main line, however this innovation fell out of use not long after.
There is a fairly complex relationship between spelling and sound. There are various issues:
Minor pauses in sentences may be marked by a comma (Thai: or , chunlaphak or luk nam), and major pauses by a period (Thai: ? or , mahap phak or chut), but most often are marked by a blank space (Thai: ?, wak). A bird's eye ? (Thai: , ta kai, officially called , fong man) formerly indicated paragraphs, but is now obsolete.
A paiyan noi ? (Thai: ) is used for abbreviation.
A paiyan yai (Thai: ) is the same as "etc." in English.
|Blue||Paired low class; has its high class counterpart|
|Purple||Single low class; turns into high class if preceded by ?|
|?-||?-?||?-||*?- > ?-, --|
|?-||?,?||-?||*-? > ?-, -|
pink:long vowel. shorten by add "?"(no ending consonant) or "-?"(with ending consonant)
green:long vowel. has a special form when shortens
|close||-? /i/||-? /i:/||-? /?/||-,-? /?:/||-? /u/||-? /u:/|
|mid||?-?,?-? /e/||?- /e:/||?- //||?-?,?-? /?:/||?-?,-- /o/||?- /o:/|
|open||?-?,?-? /?/||?- /?:/||-?,-? /a/||-? /a:/||?-,- /?/||-? /?:/|
|vowel+/a/||?- /ia/||?- /ia:/||?- /?a/||?- /?a:/||- /ua/||- /ua:/|
|/a/+vowel||?- ?- /ai/||- /a:i/||-? /am/||- /a:m/||?-? /au/||- /a:u/|
Thai (along with its sister system, Lao) lacks conjunct consonants and independent vowels, while both designs are common among Brahmic scripts (e.g., Burmese and Balinese). In scripts with conjunct consonants, each consonant has two forms: base and conjoined. Consonant clusters are represented with the two styles of consonants. The two styles may form typographical ligatures, as in Devanagari. Independent vowels are used when a syllable starts with a vowel sign.
There are 44 consonant letters representing 21 distinct consonant sounds. Duplicate consonants either correspond to sounds that existed in Old Thai at the time the alphabet was created but no longer exist (in particular, voiced obstruents such as b d g v z), or different Sanskrit and Pali consonants pronounced identically in Thai. There are in addition four consonant-vowel combination characters not included in the tally of 44.
Consonants are divided into three classes -- in alphabetical order these are middle (?, klang), high (, sung), and low (, tam) class -- as shown in the table below. These class designations reflect phonetic qualities of the sounds to which the letters originally corresponded in Old Thai. In particular, "middle" sounds were voiceless unaspirated stops; "high" sounds, voiceless aspirated stops or voiceless fricatives; "low" sounds, voiced. Subsequent sound changes have obscured the phonetic nature of these classes.[nb 1] Today, the class of a consonant without a tone mark, along with the short or long length of the accompanying vowel, determine the base accent (, pheun siang). Middle class consonants with a long vowel spell an additional four tones with one of four tone marks over the controlling consonant: mai ek, mai tho, mai tri, and mai chattawa. High and low class consonants are limited to mai ek and mai tho, as shown in the . Differing interpretations of the two marks or their absence allow low class consonants to spell tones not allowed for the corresponding high class consonant. In the case of digraphs where a low class follows a higher class consonant, often the higher class rules apply, but the marker, if used, goes over the low class one; accordingly, ? ho nam and ? o nam may be considered to be digraphs as such, as explained below the Tone table.[nb 2]
To aid learning, each consonant is traditionally associated with an acrophonic Thai word that either starts with the same sound, or features it prominently. For example, the name of the letter ? is kho khai (? ), in which kho is the sound it represents, and khai () is a word which starts with the same sound and means "egg".
Two of the consonants, ? (kho khuat) and ? (kho khon), are no longer used in written Thai, but still appear on many keyboards and in character sets. When the first Thai typewriter was developed by Edwin Hunter McFarland in 1892, there was simply no space for all characters, thus two had to be left out. Also, neither of these two letters correspond to a Sanskrit or Pali letter, and each of them, being a modified form of the letter that precedes it (compare ? and ?), has the same pronunciation and the same consonant class as the preceding letter (somewhat like the European long s). This makes them redundant.
Equivalents for romanisation are shown in the table below. Many consonants are pronounced differently at the beginning and at the end of a syllable. The entries in columns initial and final indicate the pronunciation for that consonant in the corresponding positions in a syllable. Where the entry is '-', the consonant may not be used to close a syllable. Where a combination of consonants ends a written syllable, only the first is pronounced; possible closing consonant sounds are limited to 'k', 'm', 'n', 'ng', 'p' and 't'.
Although official standards for romanisation are the Royal Thai General System of Transcription (RTGS) defined by the Royal Thai Institute, and the almost identical defined by the International Organization for Standardization, many publications use different romanisation systems. In daily practice, a bewildering variety of romanisations are used, making it difficult to know how to pronounce a word, or to judge if two words (e.g. on a map and a street sign) are actually the same. For more precise information, an equivalent from the International Phonetic Alphabet (IPA) is given as well.
|?[a]||?||kho khuat||bottle (obsolete)||kh||k||[k?]||[k?]||high|
|?||? ?||kho khwai||buffalo||kh||k||[k?]||[k?]||low|
|?[b]||?||kho khon||person (obsolete)||kh||k||[k?]||[k?]||low|
|?||? ?||cho ching||cymbals||ch||-||[t]||-||high|
|?||? ?||cho chang||elephant||ch||t||[t]||[t?]||low|
|?[c]||? ?||yo ying||woman||y||n||[j]||[n]||low|
|?||? ?||to pa-tak||goad, javelin||t||t||[t]||[t?]||mid|
|?||? ?||tho montho||Montho, character from Ramayana||th or d||t||[t?] or [d]||[t?]||low|
|?||? ?||tho phu-thao||elder||th||t||[t?]||[t?]||low|
|?||? ?||do dek||child||d||t||[d]||[t?]||mid|
|?||? ?||to tao||turtle||t||t||[t]||[t?]||mid|
|?||? ?||tho thahan||soldier||th||t||[t?]||[t?]||low|
|?||? ?||pho phueng||bee||ph||-||[p?]||-||high|
|?||?||yo yak||giant, yaksha||y||-
|?||? ?||ro ruea||boat||r||n||[r]||[n]||low|
|?||? ?||wo waen||ring||w||-[f]||[w]||-||low|
|?||? ?||so sala||pavilion, sala||s||t||[s]||[t?]||high|
|?||? ?||so rue-si||hermit||s||t||[s]||[t?]||high|
|?||? ?||so suea||tiger||s||t||[s]||[t?]||high|
|?||?||ho hip||chest, box||h||-||[h]||-||high|
|?||? ?||lo chu-la||kite||l||n||[l]||[n]||low|
|?||? ?||o ang||basin||-[g]||-||[?]||-||mid|
The consonants can be organised by place and manner of articulation according to principles of the International Phonetic Association. Thai distinguishes among three voice/aspiration patterns for plosive consonants:
Where English has only a distinction between the voiced, unaspirated /b/ and the unvoiced, aspirated /p?/, Thai distinguishes a third sound which is neither voiced nor aspirated, which occurs in English only as an allophone of /p/, approximately the sound of the p in "spin". There is similarly an alveolar /t/, /t?/, /d/ triplet. In the velar series there is a /k/, /k?/ pair and in the postalveolar series the /t?/, /t/ pair.
In each cell below, the first line indicates International Phonetic Alphabet (IPA), the second indicates the Thai characters in initial position (several letters appearing in the same box have identical pronunciation). Note how the conventional alphabetic order shown in the table above follows roughly the table below, reading the coloured blocks from right to left and top to bottom.
Pronunciation of Thai characters in initial position
Although the overall 44 Thai consonants provide 21 sounds in case of initials, the case for finals is different. Note how the consonant sounds in the table for initials collapse in the table for final sounds. At the end of a syllable, all plosives are unvoiced, unaspirated, and have no audible release. Initial affricates and fricatives become final plosives. The initial trill (?), approximant (?), and lateral approximants (?,?) are realized as a final nasal /n/.
Only 8 ending consonant sounds, as well as no ending consonant sound, are available in Thai pronunciation. Among these consonants, excluding the disused ? and ?, six (? ? ? ? ? ?) cannot be used as a final. The remaining 36 are grouped as following.
Pronunciation of Thai characters in final position
Thai vowel sounds and diphthongs are written using a mixture of vowel symbols on a consonant base. Each vowel is shown in its correct position relative to a base consonant and sometimes a final consonant as well. Note that vowels can go above, below, left of or right of the consonant, or combinations of these places. If a vowel has parts before and after the initial consonant, and the syllable starts with a consonant cluster, the split will go around the whole cluster.
Twenty-one vowel symbol elements are traditionally named, which may appear alone or in combination to form compound symbols.
(from Sanskrit visarjan?ya)
|??; ?; ?; ?; ?; ??; ??; ?; ?|
|Mai han a-kat||?; ?;|
|Mai tai khu||; ; ??; ??|
|?||?||Lak khang||??; ???; ?; ?; ??|
|?||Phinthu i||; ??; ; ?; ??; ?; ?; ?; ??; ?|
|Fon thong[a]||; ?; ??; ?|
|Fan nu[a]||?; ?; ??; ?|
|Nikkhahit||; ?; ?|
|Tin yiat||; ?|
|Tin khu||; ?|
|?||?||Mai na||??; ?; ?; ?; ?; ?; ?; ?; ?; ?; ??; ??; ?; ??; ??; ??; ?; ?; ?|
|?||Mai o||??; ?; ?|
|?||?||Tua o||??; ??; ?; ?; ??; ??; ?; ??|
|?||?||Tua yo||?; ??; ??|
|?||?||Tua wo||?; ??|
The inherent vowels are /a/ in open syllables (CV) and /o/ in closed syllables (CVC). For example, transcribes /t?àn?n/ "road". There are a few exceptions in Pali loanwords, where the inherent vowel of an open syllable is /o/. The circumfix vowels, such as ?- //, encompass a preceding consonant with an inherent vowel. For example, /p?/ is written ??, and /tap?/ "only" is written ?.
The characters ? (plus ? , which are obsolete) are usually considered as vowels, the first being a short vowel sound, and the latter, long. As alphabetical entries, ? follow ?, and themselves can be read as a combination of consonant and vowel, equivalent to (short), and (long) (and the obsolete pair as , ), respectively. Moreover, ? can act as as an integral part in many words mostly borrowed from Sanskrit such as ?? (kritsana, not kruetsana), ?? (rit, not ruet), and ?? (kritsada, not kruetsada), for example. It is also used to spell ??? angkrit England/English. The word ? (roek) is a unique case where ? is pronounced like .
The pronunciation below is indicated by the International Phonetic Alphabet and the Romanisation according to the Royal Thai Institute as well as several variant Romanisations often encountered. A very approximate equivalent is given for various regions of English speakers and surrounding areas. Dotted circles represent the positions of consonants or consonant clusters. The first one represents the initial consonant and the latter (if it exists) represents the final.
Ro han (? ) is not usually considered a vowel and is not included in the following table. It represents the sara a /a/ vowel in certain Sanskrit loanwords and appears as ?. When used without a final consonant (), /n/ is implied as the final consonant, giving [an].
|Short vowels||Long vowels|
(English RP pronunciation)
|Name||Symbol||IPA||RTGS||Variants||Similar Sound |
(English RP pronunciation)
|a||a||u||u in "nut"||Sara a||
||a:||a||ah, ar, aa||a in "father"|
||i||i||y in "greedy"||Sara i||
||i:||i||ee, ii, y||ee in "see"|
||?||ue||eu, u, uh||Can be approximated by pronouncing the oo in "look" with unrounded lips
German: the ü in Mücke
||?:||ue||eu, u||Can be approximated by pronouncing the oo in RP "goose" with unrounded lips|
||u||u||oo||oo in "shoot"||Sara u||
||u:||u||oo, uu||oo in "too"|
|e||e||e in "neck"||Sara e||
||e:||e||ay, a, ae, ai, ei||a in "lame"|
|?||ae||aeh, a||a in "at"||Sara ae||
||?:||ae||a||a in "ham"|
||o||o||oa in "boat"||Sara o||
||o:||o||or, oh, ô||o in "go"|
|?||o||o, aw||o in "not"||Sara o||
|?:||o||or, aw||aw in "saw"|
|?||Sara oe||?||oe||eu||e in "the"||Sara oe||
|oe||er, eu, ur||u in "burn"|
|Sara ia||ia?||ia||iah, ear, ie||ea in "ear" with glottal stop||?||Sara ia||?
||ia||ia||ear, ere, ie||ear in "ear"|
|Sara uea||?a?||uea||eua, ua||ure in "pure"||?||Sara uea||?
||?a||uea||eua, ua, ue||ure in "pure"|
|?||Sara ua||?||ua?||ua||ewe in "sewer"||Sara ua||
||ua||ua||uar||ewe in "newer"|
|+ ?||Sara i + wo waen||iu; iw||io||ew||ew in "few"|
|+ ?||Sara e + wo waen||?||eu; ew||eo||eu, ew||+ ?||Sara e + wo waen||e:u; e:w||eo||eu, ew||ai + ow in "rainbow"|
|+ ?||Sara ae + wo waen||?:u; ?:w||aeo||aew, eo||a in "ham" + ow in "low"|
|Sara ao[e]||au; aw||ao||aw, au, ow||ow in "cow"||+ ?||Sara a + wo waen||a:u||ao||au||ow in "now"|
|? + ?||Sara ia + wo waen||iau; iaw||iao||eaw, iew, iow||io in "trio"|
|+ ?||Sara a + yo yak||ai; aj||ai||ay||i in "hi"||+ ?||Sara a + yo yak||a:i; a:j||ai||aai, aay, ay||ye in "bye"|
|Sara ai[e]||,[f] |
|? + ?||Sara o + yo yak||?||?i; ?j||oi||oy||+ ?||Sara o + yo yak||?:i; ?:j||oi||oy||oy in "boy"|
|+ ?||Sara o + yo yak||o:i; o:j||oi||oy|
|+ ?||Sara u + yo yak||ui; uj||ui||uy|
|+ ?||Sara oe + yo yak||?:i; ?:j||oei||oey||u in "burn" + y in "boy"|
|+ ?||Sara ua + yo yak||uai; uaj||uai||uay||uoy in "buoy"|
|? + ?||Sara uea + yo yak||?ai; ?aj||ueai||uai|
|Sara am||?||am||am||um||um in "sum"|
|rue, ri, roe||ru, ri||rew in "grew", ry in "angry"||Rue||r?:||rue||ruu|
|?||Lue||?||l?||lue||lu, li||lew in "blew"||Lue||l?:||lue||lu|
Thai is a tonal language, and the script gives full information on the tones. Tones are realised in the vowels, but indicated in the script by a combination of the class of the initial consonant (high, mid or low), vowel length (long or short), closing consonant (plosive or sonorant, i.e., dead or live) and, if present, one of four tone marks, whose names derive from the names of the digits 1-4 borrowed from Pali or Sanskrit. The rules for denoting tones are shown in the following chart:
|Symbol||Name||Syllable composition and initial consonant class|
|Thai||RTGS||Vowel and final||Low||Mid||High|
long vowel or vowel plus sonorant
short vowel at end or plus plosive
long vowel plus plosive
"None", that is, no tone marker, is used with the base accent (, pheun siang). Mai tri and mai chattawa are only used with mid-class consonants.
Two consonant characters (not diacritics) are used to modify the tone:
|Low consonant||High consonant||IPA|
|Low consonant||Middle consonant||IPA|
Some dialect where words are spelled with one tone but pronounced with another often occur in informal conversation (notably the pronouns chan and khao, which are both pronounced with a high tone rather than the rising tone indicated by the script). Generally, when such words are recited or read in public, they are pronounced as spelled.
Spoken Southern Thai can have up to seven tones. When Southern Thai is written in Thai script, there are different rules for indicating spoken tone.
|Tones||Nakhon Si Thammarat accent rules||IPA|
|First tone||An initial consonant class "high" with long sound, and an initial consonant class "low" after the word.|||
|An initial consonant class "high" with short sound, and an initial consonant class "low"
with [k?], [t?], [p?] finals after the word.
|Second tone||An initial consonant class "high" both short long sound,
and an initial consonant class "low" after the word.
|Third tone||An initial consonant class "middle" long sound.|||
|An initial consonant class "middle" short sound with [k?], [t?], [p?] finals.|||
|Fourth tone||An initial consonant class "middle" both short long sound.||[?]|
|Fifth tone||An initial consonant class "low" with head word.|||
|Sixth tone||An initial consonant class "low" long sound.|||
|Seventh tone||An initial consonant class "low" short sound.|||
Other diacritics are used to indicate short vowels and silent letters:
|mai taikhu||shortens vowel|
|? or ?||thanthakhat or karan||indicates silent letter|
Fan nu means "rat teeth" and is thought as being placed in combination with short sara i and fong man to form other characters.
|"||fan nu||combined with short sara i () to make long sara ue ()|
|combined with fong man (?) to make fong man fan nu (?")|
For numerals, mostly the standard Hindu-Arabic numerals (Thai: , lek hindu arabik) are used, but Thai also has its own set of Thai numerals that are based on the Hindu-Arabic numeral system (Thai: , lek thai), which are mostly limited to government documents, election posters, license plates of military vehicles, and special entry prices for Thai nationals.
|?||pai-yan noi||marks formal phrase shortened by convention (abbreviation)|
|pai-yan yai||et cetera|
|?||mai ya-mok||preceding word or phrase is reduplicated|
|?||,||fong man, ta kai||previously marked beginning of a sentence, paragraph, or stanza (obsolete); now only marks beginning of a stanza in a poem; now also used as bullet point|
|?"||, ,||fong man fan nu, fan nu fong man, fon tong fong man||previously marked beginning of a chapter (obsolete)|
|?||?, ?, ?||angkhan diao, khan diao, khan diao||previously marked end of a sentence or stanza (obsolete)|
|?||?, ?, ?||angkhan khu, khan khu, khan khu||marks end of stanza; marks end of chapter or long section|
|angkhan wisanchani||marks end of a stanza in a poem|
|?||,||khomut, sutnarai||marks end of a chapter or document; marks end of a story|
|angkhan wisanchani khomut||marks the very end of a written work|
|?||bat||baht (the currency of Thailand)|
Pai-yan noi and angkhan diao share the same character. Sara a (-?) used in combination with other characters is called wisanchani.
Some of the characters can mark the beginning or end of a sentence, chapter, or episode of a story or of a stanza in a poem. These have changed use over time and are becoming uncommon.
|The Brahmic script and its descendants|
The Thai script (like all Indic scripts) uses a number of modifications to write Sanskrit and related languages (in particular, Pali). Pali is very closely related to Sanskrit and is the liturgical language of Thai Buddhism. In Thailand, Pali is written and studied using a slightly modified Thai script. The main difference is that each consonant is followed by an implied short a (), not the 'o', or '?' of Thai: this short a is never omitted in pronunciation, and if the vowel is not to be pronounced, then a specific symbol must be used, the pinthu (a solid dot under the consonant). This means that sara a () is never used when writing Pali, because it is always implied. For example, namo is written ? in Thai, but in Pali it is written as , because the is redundant. The Sanskrit word 'mantra' is written in Thai (and therefore pronounced mon), but is written in Sanskrit (and therefore pronounced mantra). When writing Pali, only 33 consonants and 12 vowels are used.
This is an example of a Pali text written using the Thai Sanskrit orthography ? [araha? samm?sambuddho bhagav?]. Written in modern Thai orthography, this becomes ? ? arahang sammasamphuttho phakhawa.
In Thailand, Sanskrit is read out using the Thai values for all the consonants (so ? is read as kha and not [ga]), which makes Thai spoken Sanskrit incomprehensible to sanskritists not trained in Thailand. The Sanskrit values are used in transliteration (without the diacritics), but these values are never actually used when Sanskrit is read out loud in Thailand. The vowels used in Thai are identical to Sanskrit, with the exception of ?, , ?, and , which are read using their Thai values, not their Sanskrit values. Sanskrit and Pali are not tonal languages, but in Thailand, the Thai tones are used when reading these languages out loud.
In the tables in this section, the Thai value (transliterated according to the Royal Thai system) of each letter is listed first, followed by the IAST value of each letter in square brackets. Remember that in Thailand, the IAST values are never used in pronunciation, but only sometimes in transcriptions (with the diacritics omitted). This disjoint between transcription and spoken value explains the romanisation for Sanskrit names in Thailand that many foreigners find confusing. For example, ? is romanised as Suvarnabhumi, but pronounced su-wan-na-phum. is romanised as Srinagarindra but pronounced si-nakha-rin.
Plosives (also called stops) are listed in their traditional Sanskrit order, which corresponds to Thai alphabetical order from ? to ? with three exceptions: in Thai, high-class ? is followed by two obsolete characters with no Sanskrit equivalent, high-class ? and low-class ?; low-class ? is followed by sibilant ? (low-class equivalent of high-class sibilant ? that follows ? and ?.) The table gives the Thai value first, and then the IAST (International Alphabet of Sanskrit Transliteration) value in square brackets.
|class||Sanskrit unvoiced||Sanskrit voiced|
|Thai unvoiced||Thai voiced|
None of the Sanskrit plosives are pronounced as the Thai voiced plosives, so these are not represented in the table. While letters are listed here according to their class in Sanskrit, Thai has lost the distinction between many of the consonants. So, while there is a clear distinction between ? and ? in Sanskrit, in Thai these two consonants are pronounced identically (including tone). Likewise, the Thai phonemes do not differentiate between the retroflex and dental classes, because Thai has no retroflex consonants. The equivalents of all the retroflex consonants are pronounced identically to their dental counterparts: thus ? is pronounced like ?, ? is pronounced like ?, ? is pronounced like ?, ? is pronounced like ?, and ? is pronounced like ?.
The Sanskrit unaspirated unvoiced plosives are pronounced as unaspirated unvoiced, whereas Sanskrit aspirated voiced plosives are pronounced as aspirated unvoiced.
|palatal||?||yá||? [ya] /j/||and|
Inserted sound(s) ( siat saek) follow the semi-vowel ? in alphabetical order.
Like Sanskrit, Thai has no voiced sibilant (so no 'z' or 'zh'). In modern Thai, the distinction between the three high-class consonants has been lost and all three are pronounced 'sà'; however, foreign words with a sh-sound may still be transcribed as if the Sanskrit values still hold (e.g., ang-grit for English instead of ).
?, a high-class consonant, comes next in alphabetical order, but its low-class equivalent, ?, follows similar-appearing ? as the last letter of the Thai alphabet. Like modern Hindi, the voicing has disappeared, and the letter is now pronounced like English 'h'. Like Sanskrit, this letter may only be used to start a syllable, but may not end it. (A popular beer is romanized as Singha, but in Thai is , with a karan on the ?; correct pronunciation is "sing", but foreigners to Thailand typically say "sing-ha".)
This represents the retroflex liquid of Pali and Vedic Sanskrit, which does not exist in Classical Sanskrit.
All consonants have an inherent 'a' sound, and therefore there is no need to use the ? symbol when writing Sanskrit. The Thai vowels , , , and so forth, are not used in Sanskrit. The zero consonant, ?, is unique to the Indic alphabets descended from Khmer. When it occurs in Sanskrit, it is always the zero consonant and never the vowel o [?:]. Its use in Sanskrit is therefore to write vowels that cannot be otherwise written alone: e.g., or . When ? is written on its own, then it is a carrier for the implied vowel, a [a] (equivalent to in Thai).
The vowel sign occurs in Sanskrit, but only as the combination of the pure vowels sara a with nikkhahit .
There are a number of additional symbols only used to write Sanskrit or Pali, and not used in writing Thai.
In Sanskrit, the anusv?ra indicates a certain kind of nasal sound. In Thai this is written as an open circle above the consonant, known as nikkhahit (), from Pali niggah?ta. Nasalisation does not occur in Thai, therefore, a nasal stop is always substituted: e.g. ta?, is pronounced as tang by Thai Sanskritists. If nikkhahit occurs before a consonant, then Thai uses a nasal stop of the same class: e.g. [sa?sk?ta] is read as san-sa-krit-ta (The ? following the nikkhahit is a dental-class consonant, therefore the dental-class nasal stop ? is used). For this reason, it has been suggested that in Thai, nikkhahit should be listed as a consonant. Also, traditional Pali grammars describe nikkhahit as a consonant. Nikkhahit occurs as part of the Thai vowels sara am and sara ue .
Because the Thai script is an abugida, a symbol (equivalent to vir?ma in devanagari) needs to be added to indicate that the implied vowel is not to be pronounced. This is the phinthu, which is a solid dot (also called 'Bindu' in Sanskrit) below the consonant.
Yamakkan () is an obsolete symbol used to mark the beginning of consonant clusters: e.g. phramana [br?hma?a]. Without the yamakkan, this word would be pronounced pharahamana [bar?hama?a] instead. This is a feature unique to the Thai script (other Indic scripts use a combination of ligatures, conjuncts or vir?ma to convey the same information). The symbol is obsolete because pinthu may be used to achieve the same effect?.
The means of recording visarga (final voiceless 'h') in Thai has reportedly been lost, although the character which is used to transcribe a short /a/ or to add a glottal stop after a vowel is the closest equivalent and can be seen used as a visarga in some Thai-script Sanskrit text.
Thai script was added to the Unicode Standard in October 1991 with the release of version 1.0.
The Unicode block for Thai is U+0E00-U+0E7F. It is a verbatim copy of the older TIS-620 character set which encodes the vowels ?, ?, ?, ? and ? before the consonants they follow, and thus Thai, Lao, Tai Viet and New Tai Lue are the only Brahmic scripts in Unicode that use visual order instead of logical order.
Official Unicode Consortium code chart (PDF)