The values for isotopes of strontium, carbon, and oxygen in human tooth enamel from the prehistoric site of Khok Phanom Di (ca. 21001500 BC) in Thailand shed light on human mobility and marital residence during a crucial period of subsistence change. Khok Phanom Di was a sedentary coastal community that apparently relied on hunting, gathering, and fishing in the midst of a transition to rice agriculture in the interior. The results of the isotope analyses indicate female immigration and then a marked shift to local strontium isotope signatures among females accompanied by a clear increase in the prestige of female burials. A possible explanation is a shift in the pattern of exogamy with a concomitant change in gender relations. Observation of a very similar transition at Ban Chiang, in northeastern Thailand, suggests the possibility of a regionwide social transition. In the case of Khok Phanom Di, the increasing role of females in producing high‐quality ceramic vessels may have contributed to the change.