Based on molecular and morphological data sets, we describe a new species of scincid lizard of the genus Lygosoma from Indochina, and redescribe true Lygosoma quadrupes (Linnaeus, 1766). The new species is small and slender, and represents the third member of the L. quadrupes complex, increasing the diversity of Lygosoma species recognized in Southeast Asia to 24. Based on the reevaluation of vouchered specimens from the type locality of L. quadrupes sensu Linnaeus (1766), the recognized geographic distribution of true L. quadrupes is restricted to the island of Java in Indonesia. With 10 species of Lygosoma recognized in Thailand, the country possesses considerable species-level diversity of these enigmatic, semifossorial skinks. In addition to being one of the smallest species in the genus, the new species can be distinguished from all congeners by features of its external morphology, including having small relative limb lengths, longer trunk length, and greater numbers of axilla–groin and paravertebral scale rows. Phylogenetic analyses support three divergent lineages corresponding to recognized and newly described members of the L. quadrupes complex. The descriptions underscore the need for continued and comprehensive biodiversity survey work throughout much of Southeast Asia, particularly in Indochina, where scincid diversity remains poorly understood.