Pleistocene-Holocene forager adaptations in tropical regions, including the presence and nature of a broadening diet, remain an understudied aspect of hunter-gatherer evolution. Analysis of the zooarchaeological assemblages from five Pleistocene-Holocene sites in northwest Thailand provides insight into patterns of human subsistence, adaptation, and ecological change present in highland, mainland Southeast Asia during this period. Vertebrate and invertebrate faunas from Tham Lod Rockshelter, Ban Rai Rockshelter, Spirit Cave, Steep Cliff Cave, and Banyan Valley Cave support the presence of long-term human foraging within this environment for the past 35,000 years. In this paper, we review the zooarchaeological records from these sites and identify two trends: 1) consistent and sustainable hunter-gatherer exploitation of some animals (e.g., artiodactyls, primates, turtles, and mollusks) through time, and 2) population decline and, in some cases, extirpation of certain species (e.g., goral) due to environmental changes tied to human subsistence strategies. Additionally, we find that foragers exploited resources within this region during and after the emergence of domestic plant and animal management within mainland Southeast Asia. Northwest Thailand remains an important location for understanding human adaptation in the tropics and how hunter-gatherer communities exploited resources during periods of socio-environmental change.