The issue of law governing the arbitration agreement has long been a continuously debated issue at the international level. In Thailand's situation, the Issue has yet been addressed in particular, whether through its legislations nor court decisions. The Article questions, therefore, what would be the suggested interpretative approach for Thai courts had the Issue becomes present before it? In answering the imposed question, the Article analyzes and compares relevant foreign cases, international doctrines, and academic
arguments, together with Thai specific legal context. It proposes a solution that Thai juristic methods need to be adhered to, considering in parallel the contemporary international trends on the Issue. The application of Thai juristic method first leads to the application of analogy as the third source of Thai law. However, with the application of analogy still leaving room of interpretation of what 'parties' implied choice of law' infers, reference to the fourth source of Thai law-general principles of law, sourced internationally-is required to be made. With the analyses done, the Article concludes that, in the context of Thai jurisdiction, 'parties' implied choice of law' connotes the law governing the main contract, not the law of the seat, as the law governing the arbitration agreement.