In the past, the King governed the country through absolute monarchy-the oldest form of monarchy of Thailand. During the Sukhothai era (1181-1474), under the ruling by King Ramkhamheang (1279-1298), people could lodge a petition to the King by ringing a bell near the town hall to have their grievance redressed. The King himself would require and judge. Later, as the gap between the ruler and citizens became increasingly larger, and the public administration became more sophisticated. There was an initiation to transfer the ruling power from the administrative branch to people by deploying special legislative institutes to investigate and redress grievances of people.
The term “Ombudsman” was first mentioned in the draft Constitution B.E. 2517 by the Constitutional Drafting Committee. (The legal mandate of the Ombudsman was described in the draft Constitution.) However, the National Legislative Assembly decided to remove this section from the Constitution during the revision process.
On 16 February 1990, the Governing Committee and the House of Representatives Affairs Committee in collaboration with the Institute of Public Policy Studies, the Social Science Association of Thailand organized a seminar on the Parliamentary Ombudsman. There were approximately 80 experts attended the seminar. This was the first time that an official brainstorming was held to set a guideline for the establishment of the Parliamentary Ombudsman.
Since then, there have been more seminars, discussions and publicizing of the concepts through mass media concepts, but these concepts were merely recognized by members of parliament, academics and experts. After that, in 1987, there was a strong drive to regulate the Parliamentary Ombudsman in the constitution of Thailand by amending the Constitution of the Kingdom of Thailand B.E. 2534 (1991), Issue 5 B.E. 2538 (1995) as provided in Section 162 bis as follows:
“The King shall appoint not more than five Parliamentary Ombudsmen by following the resolution of the Parliament. The President of the Parliament shall be countersign the Royal Command appointing the Parliamentary Ombudsman.”
Since there was not any regulation stipulating duration of the operation, therefore, during the period that the said constitution was effective, no Parliamentary Ombudsmen were appointed.
However, after the repulsion for political reform until it led to the amendment of the Constitution of the Kingdom of Thailand B.E.2534 (1991), Issue 6 with a further amendment in B.E.2539 (1996). The amendment was made in Section 211 on the establishment of the Constitution Drafting Committee and the establishment of the Ombudsman consequently brought to the success under the name "Parliamentary Ombudsman" provided in the Constitution of the Kingdom of Thailand, Section 197, Section 6 Parliament, Part 7 the Parliamentary Ombudsman, Section 196, 197 and 198. Also, there was the enactment of the Organic Act on Parliamentary Ombudsman to support and define practical details for implementation which were approved by the parliament. It was eventually promulgated as the Organic Act on the Parliamentary Ombudsman B.E. 2542 (1999).
On 1 April 2000, there was a royal command which appointed Mr. Pichet Soontornpipit as the first Parliamentary Ombudsman of Thailand. And on 12 April 2000, there was an order of the Parliamentary Ombudsman appointing Mr. Pramote Chotimongkol as the first Secretary-General, Office of the Parliamentary Ombudsman and set the date 12 April 2000 was considered to be the establishment day of the Parliamentary Ombudsman. Later, Mr. Poolsap Piyanan and General Theeradech Miphian were selected to be the Parliamentary Ombudsmen. (General Theeradech Miphian was the first Chief Ombudsman)
Later, on 19 September, 2006, a coup d'état occurred by a group of people called
"Council for Democratic Reform” (CDR). CDR announced the abrogation of the Constitution of the Kingdom of Thailand B.E. 2540 (1997). As a result, the Organic Act would have been automatically repealed. However, there was the 14th announcement of the CDR dated 21 September 2006 for the Parliamentary Ombudsman provided that "To facilitate continuity of complaint handling and the public administration and the performance of state officials, CDR announces that the Organic Act on Parliamentary Ombudsman B.E. 2542 (1999) shall be effective until it is otherwise provided.", which allowed the Parliamentary Ombudsman to continue to perform duties to redress grievance of people.
After the abrogation of the Constitution of the Kingdom of Thailand B.E. 2540 (1997) was abolished, there was an enactment of the Constitution of the Kingdom of Thailand (Interim) B.E. 2549 (2006) to draft the new issue of the Constitution for ruling the country. All people were able to participate in expressing opinions in every step. After the completion of the draft constitution, a referendum was held. The result showed that majority of people agreed to adopt the draft constitution, which was announced to be the Constitution of the Kingdom of Thailand B.E. 2550 (2007) on 24 August 2007 of which the Parliamentary Ombudsman mechanism was still effective in the Constitution as an independent organization under the Constitution to further investigate the exercise of state power. Additional duties and powers were also granted and the name was changed from "Parliamentary Ombudsman" to "Ombudsman".
In 2009, the Organic Act on the Ombudsman B.E. 2552 (2009) has been announced.
On 22 May 2014, the notification of the National Council for Peace and Order No. 11/2014 regarding the termination of the Constitution of the Kingdom of Thailand was announced but still the independent organizations and other organizations under the Constitution B.E. 2550 (2007) were still remained to continue performing their duties.
On 6 April 2017, the Constitution of the Kingdom of Thailand B.E. 2560 (2017) was enacted. Duties and power of the Ombudsman are prescribed in the Constitution of the Kingdom of Thailand B.E. 2560 as follows:
(1) to recommend the relevant State agencies to revise any law, rule, regulations, rules or order or any operative procedure that causes grievance or unfairness or imposes an unnecessary or undue burden on the people;
(2) to conduct fact-finding when it is found that there is a person affected by grievance or unfairness arisen from non-compliance with the law or ultra vires acts of a State agency or State officials in order to recommend the relevant State agencies to eliminate or deter such grievance or unfairness;
(3) to submit the Council or Ministers for acknowledgement that a State agency has not yet correctly and completely complied with Chapter V Duties of the State.