Resin bees of the subgenus Ranthidiellum , are rare and endemic to Southeast Asia. These bees are known to construct resinous entrance tubes to their nests. Here, the new species Anthidiellum ( R.) phuchongensis sp. nov. is described along with a description of its nest collected from Phu Chong Na Yoy National Park, Ubon Ratchathani Province, Thailand. In addition, the bee cleptoparasite, Stelis ( Malanthidium) flavofuscinular sp. nov., and the male of A. ( R.) ignotum Engel, 2009, are described for the first time. A key to Ranthidiellum species is also provided.