The first enactment known in the history of Thailand on audit and control of public finance dated back to 1875 when the Royal Audit Office created by Royal Decree was proclaimed by the late King Chulalongkorn , the fifth King of the present dynasty, with independent power and duty over the control of public finance. The Royal Audit Office was responsible only to the then absolute monarch.
Since then, the audit of public accounts and financial control of public funds has enjoyed an independent exercise of its functions inspite of various subsequent modifications to the first enactment. The principle of independence of the auditor of public accounts has remained unaltered to the present day.
Both the Legislature and the Government are fully aware that it is the independence of the auditing institution and the sufficient safeguard of its power and duty that will assist them in the control and performance of their financial prerogatives and obligations. Moreover, both bodies have also found that for the auditing institution to perform its role successfully, it is not enough to have only undoubted organic independence. It is of utmost importance that the auditing institution have conditions in which it uses its independence as appropriate and necessary for the proper discharge of audit responsibilities.
From this base, the Audit Council Act 1933 was enacted. The Act established the Audit Council of Thailand as the government agency responsible for auditing government accounts, under the direction of its President. The Act abolished Department of Audit which had been created in the Ministry of Finance in 1915 and consolidated its powers and duties in the new establishment.
The Audit Council was considered to be an independent body fully independent of other executive authority and solely responsible for setting its own direction and scope of audit without interference. Since the end of 1972 the President has reported directly to the Prime Minister, whereas previously he reported only to the Office of the Prime Minister.
To revise the law on the Audit Council, the State Audit Act 1979 was enacted and became effective on March 1,1979. The Act made several changes. It changed the title of the office to the Office of the Auditor General of Thailand (OAG) . This, of course, changed the title of its head to Auditor General. It authorized the OAG to extend its scope beyond financial audits to assessment of economy, efficiency, and effectiveness, and to audit to assessmentto audit the collection of taxes, fees and other incomes of the audited agencies.