During the Permian, areas on the western rim of Indochina terrane were parts of the Paleotethys; therefore, the Permian rocks exposed in central and northeastern Thailand are composed mainly of limestones with less siliciclastic rocks. Diversified fossils such as fusulinaceans, corals, brachiopods, conodonts recovered from these limestones and shales have been recorded for more than 50 years. Recently ostracods are recovered from limestones of Saraburi Group. Seventeen sections of Lower to Middle Permian located in Loei, Phetchabun, Nakhon Sawan, and Lopburi provinces were investigated. More than 200 species are identified, most are endemic. The ostracod assemblages including Bairdiidae, Acratiidae, Sigilloidae, Geroiidae, Cytherideidae, Cavellinidae, Polycopidae, Aparchitidae, Kloedenelidae, Knoxitidae, Paraparchitidae, Kirkbyidae, Amphissitidae, Youngiellidae, Hollinellidae, Coelonellidae are typical shallow marine species inhabiting on marginal marine to exterior platform environments. Thirty-one species are known from other sites within Paleotethys region and are also benthic inhabitants. Provincialism index suggests that the Early Permian ostracods from Thailand have close relationships with those reported from Eastern China, and the Middle Permian ones have relationships with Tunisia, South China, and Eastern China species.