An administrative code and a national framework of administrative courts was established under the 1997 Constitution but the origins of the contemporary system of administrative justice in Thailand go back to well over a century earlier. This essay will consider the relationship between the emergence of a relatively centralised state in the nineteenth century and the provision of an identifiable system of administrative law in Thailand. It will be argued that the episodic development of administrative justice can be related to a range of diverse elements including: the initial foundation of the Council of State during the reign King Rama V; an interest in European law and legal systems; the recognition of a principle of legality under the influence of Pridi Banomyong as part of a transition from absolute to monarchy to constitutional monarchy; the impact of the Council of State Act of 1933, which led to the establishment of a Petitioning Council under the Thai Council of State to handle grievances and provide remedies for Thai citizens.