Burma and Thailand are inhabited by 14 species of Mastacembelidae, eight Macrognathus and six Mastacembelus. Two new species of Macrognathus are described from Thailand, one with rostral toothplates and one without. Mastacembelus dayi, known only from Burma, is a valid species related to M. alboguttatus; Mastacembelus favus, from Thailand and Western Malaysia, is distinct from its close relative M. armatus.
