Historically, in the Sukhothai period, (A.D. 1238 – 1350) the King was the “Fountain of Justice” where the King personally decided all disputes. Sometimes his authority was delegated to councilors under his closed scrutiny, thus, this royal supreme authority was never fully discharged to others. Early in the Rattanakosin Era, the executive and judicial power was not yet separated, the adjudication of cases was the responsibility of different government entities. Generally speaking, courts were scattered among several departments whose officials could act as the judges deciding cases. In 1782, the laws derived from the Ayutthaya period were revised and completed in 1805 resulting in the written form of law called “The Law of Three Seals.” It had been the authority of the land until the reign of King Rama V, where a reform of legal and court system was introduced together with an open door policy of trading with foreign nations.
In 1882, King Rama V founded the first building of the Court of Justice. Later, in 1892, the Ministry of Justice was established and brought about the centralization of all Courts of Justice. Meanwhile, the first law code was promulgated in 1908 on criminal law. The founder of modern Thai law was Prince Rabi of Ratchaburi who played a leading role in introducing a modern system of judicial administration. The drafting of the Civil and Commercial Code was stared in the reign of King Rama V and was during the reign of King Rama VII. The Revolution of 1932 had an important effect on the Thai legal and judiciary system since it changed the form of government from an absolute monarchy to a constitutional monarchy. The Constitution vested the judiciary power with the Courts. Judges perform their duties in the name of the King and are assured of independence in adjudicating case according to the law.