This article is to analyze indirect speech acts of interrogative sentences in Thai language based upon Austine’s speech acts theory. One of the things that foreign language learners should not overlook for communicative competence is the acquisition of pragmatic skills, especially indirect speech acts. As a way to acquire such pragmatic ability, this article tried to help Thai language learners to communicate more effectively by analyzing and examining the form of Thai language interrogative sentences performing indirect speech acts. To this aim, in this article, the definition of speech acts, the definition of indirect speech acts, and the function of indirect speech acts were first studied, and the types of interrogative sentences in Thai language and the classification of interrogative sentences in Thai language were also examined. Based on this, interrogative sentences in Thai language were divided into wh-questions, yes-no questions and alternative questions, and when each question form performed an indirect speech act, its function was divided into a directive function, an assertive function, and an expression function, and the aspects and characteristics were described as examples.