Although the formation and development of economic regionalism promoted by Thailand have demonstrated some movement towards a deeper economic integration in ASEAN that had been predicted by the Eurocentric theories, it is evident that Thailand's economic regionalism has not developed in a linear fashion. Indeed, the nation's ambitious commitment as a vigorous supporter of ASEAN economic cooperation has been interrupted by backtracking and delaying commitments to economic regionalism. This inconsistent involvement of Thailand in ASEAN has challenged the rationale of the Eurocentric theories, which claim economic interests as the basis for deepening economic integration. Since their focus on an economically oriented rationale limits the capacity to understand political and other causes (and consequences) of economic regionalism, they could not sufficiently explain the case of Thailand's unsteady progress towards regional consolidation. Particularly, the Eurocentric theories struggle to explain why different administration periods have interpreted economic interests differently and why economic interests have not always been the major cause for pursuing economic regionalism. Given the inadequacy of Eurocentric theories, this article attempts to explore an alternative explanation of Thailand's inconsistent involvement in economic regionalism by focusing on the ASEAN Free‐Trade Area. The article applies the domestic coalition approach with a divergent institutional configuration. Instead of an economically oriented rationale, the study suggests that the rationale for deeper economic regionalism with ambitious commitment has hinged upon the liberal‐minded coalition of dominant actors, along with the relative centralization of domestic political institutions.