As the 5th part of the serial studies on the genus Lecithocera Herrich-Schäffer of Thailand, nine additional species including six new species: L. gilviana sp. nov., L. orbiculata sp. nov., L. tumidosa sp. nov., L. calomerida sp. nov., L. poculata sp. nov., and L. eremiodes sp. nov., are reported in this paper. Three species, L. mylitacha Herrich-Schäffer, L. castanoma Wu, and L. squalida Gozmány, are first reported from Thailand, and the females of them are newly found since the species were described. Images of adults, venation, and the male and female genitalia of the known species are given.
