This chapter looks at the impact of investment treaties on the rule of law in Thailand. The contention of this chapter is that it is difficult to ascertain clear evidence to support the conclusion that investment treaties have had wider effects on governance in Thailand – whether in terms of positively improving domestic institutions or negatively chilling government decision-making and the exercise of regulatory power. However, the evidence shows some efforts by relevant agencies in the Thai government to internalise the state’s investment treaty obligations. The chapter proceeds in three main parts. First, an overview of investment treaty policy in Thailand and the process for the conclusion of investment treaties are presented. Second, it appraises the internalisation process of investment treaty obligations and potential challenges to internalisation with reference to concrete examples. Third, it analyses the rule of law impact of investment treaties by considering the extent to which investment treaty obligations as well as the first treaty claim have “improved” or “constrained” the conduct of the government.