This article critically re-examines some of the major hypotheses about the assimilation process in general and the assimilation of the Chinese in Thailand in particular. We argue that assimilation cannot be seen as a straight line, one-way, lineal process of the Chinese becoming Thai. At the very least, we suggest that assimilation be conceived as a two-way process which, in the long run, will leave the Chinese with something Thai and the Thai with something Chinese. The important theoretical question is no longer whether the Chinese in Thailand have been assimilated or not, but rather how they, as individuals and as a group, go about presenting themselves in their transactions with the Thai and other Chinese, and why. The analytical focus will thus be on the dynamics of social transactions within and between ethnic boundaries. What typically happens when an ethnic actor stays within his or her own ethnic boundary? What motivates him or her to cross it? The primordialists on the one hand and the situationists on the other answer these questions in seemingly contrasting ways. We maintain in this article that this need not be so. It is our suggestion that some fundamental, classical dichotomies in sociology, such as instrumental and expressive functions, public and private place, and secondary and primary status, be retrieved and used creatively as strategic conceptual building blocks in the overall task of theory-building in the field of ethnic studies.