The hitherto monotypic opilionid genus Fangensis Rambla, 1994 is re-evaluated from new material collected in northern, western and southern Thailand. The original description of F. leclerci Rambla (type material not traceable) was based on specimens belonging to at least three distinct species. Fangensis leclerci is thus redefined and the binomen restricted to specimens from a cave in northern Thailand only. Three new species are described, F. spelaeus, sp. nov. and F. cavernarus, sp. nov. from two caves in western Thailand and F. insulanus, sp. nov. from forests on two islands in southern Thailand. Taxonomic characters are discussed and relationships among Fangensis species and between Fangensis and other cyphophthalmids are evaluated using morphological data and ~4 Kb of molecular data from three loci, two nuclear ribosomal genes and a mitochondrial coding gene. Overall, data indicate monophyly of Stylocellidae and morphological and ribosomal data suggest monophyly of Fangensis, which is in turn divided into two clades, one composed of the three species from northern and western Thailand and the other represented by the species from southern Thailand. Observations on mating in F. leclerci are provided.