This paper provides a comprehensive and updated catalogue of the mammalian type specimens (four holotypes and 21 paratypes) deposited in the Natural History Museum Thailand (THNHM), National Science Museum. Documenting and maintaining type collections is critical for ensuring zoological nomenclatural stability, providing an immutable reference resource for worldwide taxonomic and systematicstudies,and establishingverified biodiversity databases. This catalogue covers four species belonging to three families: Hipposideros halophyllus Hill and Yenbutra, 1984 (Hipposideridae), Hipposideros lekaguli Thonglongya and Hill, 1974 (Hipposideridae), Megaerops niphanae Yenbutra and Felten, 1983 (Pteropodidae), and Niviventer hinpoon (Marshall, 1976) (Muridae), representing the complete set of mammalian type materials currently housed at THNHM. We present granular data regarding specimen labeling, reference materials, collection periods (spanning 1973 to 1978), geographic coverage (Central, Northeast, and Northern Thailand), and historical collector associations. The methodology involved meticulous examination of physical specimens, cross-referencing with original species descriptions to validate nomenclatural authenticity, and correcting typographical errors against the primary collection databases to preserve historical and scientific accuracy. Ultimately, this unified inventory serves as an essential reference archive supporting future systematic, ecological, and evolutionary research in Southeast Asian mammalogy.