Dinogamasus saengdaoae Attasopa & Ferrari sp. nov. is described based on adult females from the abdominal pouch of females of Xylocopa tenuiscapa (Westwood) in Chiang Mai Province, Northern Thailand. The new species belongs to the D. perkinsi (Oudemans) group (sensu LeVeque) and can be distinguished from its congeners by the combination of the following characters: (1) dorsal shield covering opisthosoma neither laterally nor posteriorly; (2) opisthonotal soft cuticle with a pair of relatively long setae posteriorly; (3) setae pd1, pd2 on genu I and ad3, pd3, pl1, pl2 on both genu and tibia I conical. Maximum likelihood-based analysis of newly-generated DNA barcodes shows that the sequenced specimens of D. saengdaoaesp. nov. form a monophyletic cluster, and parsimony analysis of a previously available morphological dataset indicates that the species comprises a strongly-supported clade with D. perkinsi and D. piperi LeVeque. We provide an additional couplet for Lundqvist's key for the species of Dinogamasus Kramer to facilitate identification of D. saengdaoaesp. nov..