A new species of webspinner, Eosembia apterosa Poolprasert and Edgerly, n. sp., from Chiang Mai Province in Thailand, is described and illustrated. The new species is distinguished from previously described Eosembia by the occurrence of winglessness in the males. Beyond just winglessness, other morphological characters of the unidentified specimens when compared to E. auripecta Ross and E. aequicercata Ross suggest that they represent a new species. We present the description of the new species, along with a distribution map and key to the currently known species of SE Asian Eosembia.