Ten taxa of small carpenter bees belonging to subgenus Ceratinidia Cockerell and Porter, 1899, of the genus Ceratina Latreille, 1802, are recorded from Thailand. One new species, C. chiangmaiensis, is described. Ceratina lepida var. sutepensis Cockerell is elevated to full species status as C. sutepensis Cockerell. Ceratina lepida var. sublepida is synonymized under C. sutepensis. Lectotypes are designated for Ceratina cognata Smith, C. compacta Smith, and C. sutepensis Cockerell. Collecting records and brief taxonomic comments on Ceratinidia species in Thailand are presented, together with keys to the species.