In the mid-nineteenth century, as part of Thailand's modernization programme, Thai elites embarked on the conscious construction of a Thai national identity, which included the promulgation of three central elements: chāt [nation], sādsnā [religion] and Phra Mahāgasat [monarchy]. Essentially, these elements came to mean Central Thai ethnicity and the Buddhist religion. This paper seeks to assess the effects of Thai nationalism on ethnic relations in Thailand with an evaluation of the ethnic composition of income inequality. It specifically tests a structuralist model of social exclusion using a variety of quantitative empirical tests that rely on survey and census data in order to uncover the dynamics of Thai nationalism's effect on ethnic economic inequality. The paper ends with suggestions for a new approach to Thai nationalism.