The study of macaque monkeys harbors advancements in the field of biomedical research. It is imperative to understand the genetic composition of different species of macaques to assess their accuracy as non-human primate (NHP) models for disease detection and treatment assessments. We sought to characterize the hybridization and admixture of the Southeast Asian macaques using single nucleotide polymorphism markers and analyzing the populations on the mainland and the island. Using AMOVA tests and STRUCTURE analysis, we determined that there are three distinct populations: Macaca mulatta, M. fascicularis fascicularis, and M. f. aurea. Furthermore, the island species holds an isolated population of M. f. aurea that demonstrate high inbreeding and genetic uniqueness compared to the mainland species. Findings from this study confirm that NHP models may need to be modified or updated according to changing allelic frequencies and genetic drift.