A latest Permian radiolarian fauna is described from a chert-clastic sequence exposed at Khao Wang Chik, Klaeng, eastern Thailand. This fauna was recovered from a continuous siliceous sequence comprised of white to light gray siliceous shale, dark gray bedded chert, and dark gray siliceous shale. The fauna is composed of Neoalbaillella optima, Albaillella levis, A. triangularis, Entactinia itsukaichiensis, Triaenosphaera minuta, Ishigaum trifustis, Nazarovella inflata, Triplanospongos musashiensis, Copicyntra akikawaensis and others. These radiolarians represent the latest Permian Neoalbaillella optima Assemblage reported from Japan, Russian Far East, Philippines, south and southwestern China, and northern Thailand. The radiolarian-bearing sequence was probably deposited in the deep, pelagic environment of the Paleotethys Ocean. An overlying coarse-grained clastic sequence reflects an abrupt change in local depositional environment, possibly caused by the narrowing of the Paleotethys Ocean in Early Triassic time. Twenty-eight radiolarian species belonging to 15 genera are systematically investigated. One new genus, Klaengspongus, and four new species, Triaenosphaera longispina, Ishigaum klaengensis, Pseudospongoprunum? fontainei, and Klaengspongus spinosus are described.