The syntactic parallelism between Thai and Cambodian is striking. Not only is the order and inventory of individual form classes almost identical, but also many semantically equivalent forms seem to share identical ranges of syntactic occurrence. Given syntactic similarity of such range and magnitude, there are three possible explanations: 1) Genetic relationship. In spite of their syntactic similarity, Thai and Cambodian are not, so far as has been demonstrated by traditional methods of comparative reconstruction, genetically related. 2) Coincidence. When one considers the number of different syntactic relations occurring in the same order in the two languages, the probability of change convergence is infinitesimal.