Thailand has been extensively surveyed for aquatic insects in the last two decades. However, other than descriptions of adults, the family Psephenidae have gone unexamined. Previously, 13 genera and 26 species of adult psephenids were known from Thailand. In our survey for larval psephenids, we found all genera of Eubrianacinae previously known from Thailand plus Mubrianax Lee, Satô, and Yang, a new country record, and one undescribed larva. In Eubriinae, we found larvae of three of the five genera known from Thailand, plus Homoeogenus Waterhouse, a new country record. In Psepheninae, we collected larvae of Mataeopsephus Waterhouse, a new country record. In Psephenoidinae, we were able to identify only Sinopsephenoides Yang, although we have numerous records of unidentified larvae in the subfamily. New locality information is provided plus a key to the subfamilies and genera for all known psephenid larvae from Thailand.