Cognomen Sompoj (สมพจน์ 
, Sompoj 
) , in all the world, is a very rare family name. The last name Sompoj is characteristic of South-eastern Asia, particularly Thailand, where it is a very rare surname. Much more frequently, Sompoj is the forename as well as the last name.
Chanla, Intarakumhaeng, Boonsathienwong, Chatrattichai, Jaturanratsamee, Lerthanawat, Kajonpradabkul, Chumchujan, Chaowakunakorn, Saiboonruen, Wongratpanya, Letthanawat, Rakthangtham, Kliangket, Chansamut, Chantadee, Udomnilobon, Ersamarn, Pongun, Tanson, Vutiboonyawatana, Pothong, Lakngoenchai, Somkaney, Techaboonako, Chimngam, Kulwijith, Kwunsung, Tananingul, Tanvirachaisakul, Tapaamornkit, Tachamena, Khunwang, and Chandraprabha