A 727 m thick sequence of the Lower and Mid Palaeozoic in Satun province, south peninsular Thailand is represented by a continuous succession of deeper water carbonates and clastic rocks ranging from the Caradoc to the Silurian, conformably overlain by the shallower water carbonates and clastic rocks of the Devonian. At least five lithostratigraphic units have been recognised and are formalised here as the Pa Kae Formation, Wang Tong Formation, Kuan Tung Formation, Pa Samed Formation and Khao Chu Nong Formation. The Pa Kae Formation, proposed for the uppermost formation of the Thung Song Group, is made up of a rhythmically interbedded sequence of red weathering (?) grey nodular limestone and dark red argillaceous layers with coarse stromatolitic polygons. This contains an Upper Caradoc-Lower Ashgill trilobite fauna and was probably deposited in deep water. The conformably overlying Wang Tong Formation consists principally of black carbonaceous, graptolitic shale and thin bedded chert, interfingering with dark grey to light grey, micaceous siltstone with Dalmanitina and white-grey graptolitic mudstone. Pyrite nodules are common. The Ordovician-Silurian boundary is placed in the lower part of this formation above the Dalmanitina beds. The Kuan Tung Formation is thin bedded grey and pink limestone with brown argillaceous layers. It changes laterally to red nodular limestone over a short distance. An Emsian conodont fauna is found at the top of the middle member of the Kuan Tung Formation. The Pa Samed Formation consists of a black tentaculitic shale, reddish brown to brown, well bedded, laminated feldspathic sandstone interbedded with red shale, decalcified shale or argillaceous limestone, brownish grey massively bedded sandstone, and brown feldspathic sandstone with grey shale lenses. The youngest unit is a peritidal to shallow subtidal limestone of the Khao Chu Nong Formation, of probable middle-late Devonian age. These formations display a gradual shallowing of the depositional environment from deep marine during the Upper Caradoc through the Mid Devonian, with a short interval of slight shallowing in the Emsian, to shallow marine during the Mid-Upper Devonian.