Survey work in the evergreen forests of Khao Nan National Park, Nakhon Si Thammarat Province, Thailand during 2007-2009 resulted in 13 species of Olethreutini belonging to 9 genera. Among these, Gnathmocerodes tonsoria and Sorolopha argyropa are recorded for the first time from Thailand. Diagnoses and photographs of adults and genitalia structures are provided for each species.