Three new species, Amasa beaveri sp. nov., Amasa cognatoi sp. nov., and Amasa macarthorum sp. nov., are described. Three species, Amasa circumcisula (Schedl, 1954), Amasa dasyura (Browne, 1950) and Amasa latetruncata (Schedl, 1942), are recorded in Thailand for the first time. A synoptic list of the Thai fauna with distributions is also provided.