The law part of corruption is that it prohibits a certain behaviour of a public official in abusing his or her own office for personal gain, whereas the economics part evaluates the trade-off and efficiency of the economic causes and consequences of legal rules on corruption. Using Thailand as a background, this paper makes a reference to the legal and political role of the state according to the Social Contract Theory, the Principle of the Separation of Powers of John Locke, J J Rousseau, and Montesquieu, and the Economic Approach of Crime and Punishment of Professor Gary Becker, to explain the establishment of anti-corruption policies and practices in Thailand. It goes on to comment on the strengths and weaknesses of the most important anti-corruption organisation of the country, the National Anti-Corruption Commission (NACC), and compares this with similar organisations in other East and Southeast Asian countries, namely Hong Kong, Indonesia, Malaysia, and the Philippines. The paper concludes with policy implications on the improvement of anti-corruption activities based on greater efficiency of many measures for corruption suppression and prevention.