The micro land snail genus Diplommatina (family Diplommatinidae) is widely distributed in Southeast Asia and includes many endemic species. Three new species of Diplommatina are described from Satun Province in southern Thailand. Diplommatina bulonensis sp. nov., D. laemsonensis sp. nov. and D. prakaiphetensis sp. nov. are distinguished from other species in the genus by their shell size and shape, the number of radial ribs on the penultimate whorl, the number of whorls, and features of the peristome. The agreement between phylogenetic tree based on analyses of COI and 16S sequences and comparative morphology support the delineation of these new species which, when compared to related species, belong to well-differentiated clades. The K2P distance between any of the three new species and other Diplommatina species included in the molecular phylogenetic analysis was at least 5.5% in COI and 3.9% in 16S. Two of the three new species (D. prakaiphetensis sp. nov. and D. bulonensis sp. nov.) are apparently endemic to Prakaiphet Hill and Bulon Pai Island, respectively. Additionally, we documented a new regional record for D. naiyanetri in Satun Province. These new species and records contribute to the knowledge of Thailand’s land snail biodiversity and highlight the need of conservation protections for regional karst habitats.