Resin bees of the genus Megachile subgenus Callomegachile sensu lato ( Hymenoptera ; Megachilidae ) from Thailand are reviewed. The 14 species treated include those described or revised in the subgenus Alocanthedon , a junior synonym of Callomegachile (three species), and in Carinula (one species). One new species is described, Megachile chiangmaiensis Chatthanabun and Warrit, sp. nov. The replacement name Megachile parornata Chatthanabun, Warrit and Ascher, nom. nov., is proposed for M. gigas Wu (not Schrottky), which is recorded for the first time outside China. For each species, maps and full label data for the examined material documenting occurrences in Thailand are provided. In addition, global ranges, floral associations, and other life history data are summarized and a key to the Thai species is provided for females.