Geologic mapping and subsurface lithostratigraphic investigations Tt ere carried out in the Khao Pun area (4 km(2)), central Thailand. More than 250 hand specimens, 70 rock slabs, and 70 thin sections were studied in conjunction with geochemical data in order to elucidate paleoenvironments and tectonic setting of the Permian marine sedimental uv sequences. This sedimentary succession (2485 m thick) was re-accessed and re-grouped into three lithostratigraphic units, namely in ascending order the Phu Phe, Khao Sung and Khao Pun Formations. The Lower to lower Upper Permian sedimentary facies indicated the transgressive/regressive succession of shelf sea/platform environment to pelagic or abyssal environment below the carbonate compensation depth. The sedimentological and paleontological aspects, together with petrochemical and lithological points of view reveal that the oldest unit might indicate an Early Permian shelter ed shallow or lagoonal environment. Then the depositional basin became deeper as suggested by the prolonged occurrence of bedded chert-limestone intercalation with the local exposure of shallower carbonate build-up. Following this, the depositional environment changed to pelagic deposition, as indicated by laminated radiolarian (e.g. Follicucullus sp.) cher ts. This cryptic evidence might indicate the abyssal environment during middle Middle to early Late Permian; whereas, previous studies advocated shelf-facies environments. Following this, the depositional condition might be a major regression on the microcontinent close to Indochina, from the minor transgressive/regressive cycles that developed within a skeletal barrier; and, through the lagoon with limited circulational and anaerobic conditions, on to the tidal fiat to the sheltered lagoon without effective land-derived sediments.