The state agencies (Thai: ) that form Thailand's public sector consist of several types of functioning bodies. While some agencies established by mandate of the constitution are independent, others are directly or indirectly answerable to the executive of the Royal Thai Government. The majority of these are government agencies, which employ the civil service as well as the military. Others include public organizations and state enterprises.
In addition to the constituents of the three branches of government, the (now-repealed) 2007 constitution provided for certain regulatory and advisory bodies. For further details, see Constitutional organizations of Thailand.
Government agencies under direct control of the ministries are the oldest type of state agency. They date to the establishment of the modern bureaucracy by King Chulalongkorn in the 19th century, while state enterprises were introduced in the first half of the 20th century.
By the 1990s, the bureaucratic structure of government agencies had become recognized as a source of inefficiency, and administrative reforms begun in 1997 sought to ameliorate the issue by creating new forms of state agencies with greater autonomy and operational flexibility. Thailand's state agencies now fall into the following types, as classified by the Office of the Public Sector Development Commission:
Government agencies (?) make up the majority of the machinery of government. They serve the basic functions of government, providing administrative public services, and follow the policies of the executive. Their operation is based on the laws and regulations of the civil service and the military.
Within the central administration, government agencies include the ministries (?) and sub-ministries (?), and their constituent departments () or equivalent agencies. Within the provincial administration, they include the provinces and their districts. Within the local administration, they include the administrative organizations of local governments, including provincial administration organizations, municipalities and subdistrict administration organizations.
State enterprises () provide industrial and commercial public services. They exist both as purpose-established organizations (e.g., the State Railway of Thailand) and limited companies in which the government is the majority shareholder (e.g., Krung Thai Bank PLC).
Public organizations (), also known as autonomous public organizations, were introduced in 1999. They provide social and cultural public services, and operate under supervision of the government, while maintaining a greater degree of administrative independence.
Most newer public organizations are established under the Public Organization Act, B.E. 2542 (1999 CE), the first being Banphaeo Hospital in 2000. Others, such as the National Science and Technology Development Agency, are established by respective acts of parliament, and are also referred to as autonomous agencies. Autonomous universities (as opposed to those that function as government agencies) also fall under this category.
Independent administrative organizations () serve the operations of regulatory bodies (e.g., the Office of the National Broadcasting and Telecommunications Commission) or other public agencies whose independence is in the public interest (e.g., the Thai Public Broadcasting Service).
Legal-entity funds (?) are established by acts of parliament to serve certain economic purposes that are of public benefit.
Service delivery units (?) were introduced in 2005. They are service-oriented, quasi-autonomous units operating under government departments, but have a more flexible internal management system. Their services are primarily aimed for their mother agency.
In 2017, several government agencies were transferred to the direct control of the king, and ceased to be considered state agencies. They were the Bureau of the Royal Household (previously a ministry-independent department) and its subsidiary the Office of His Majesty's Principal Private Secretary, the Royal Aide de Camp Department and the Royal Guard Command (previously under the Ministry of Defence), and the Royal Court Security Police (previously under the Royal Thai Police).