The ethnic group was first known to Westerners in the 1920s, when the language was already considered in severe decline. In the 1970s, a linguist began working on the language in the several areas where it was still used, by which time it was already extinct in two of the locations given by the surveyor 50 years earlier. The people were then forced from two of these villages when the Electricity Generating Authority of Thailand built dams over the Kwae Yai and Khwae Noi River. Because of the displacement of the people of an already declining language, the language is considered especially vulnerable to extinction. The last children speakers were in the 1970s, and the children now speak Thai as their first language.
Bradley, David. "The Disappearance of the Ugong in Thailand", in Investigating Obsolescence: Studies in Language Contraction and Death, Nancy C. Dorian, ed. Cambridge: Cambridge University Press, 1992. pp 33–40