Thailand / China: Yao shaman's mask from northern Thailand. The Yao nationality (its great majority branch is also known as Mien) is a government classification for various minorities in China. They form one of the 55 ethnic minority groups officially recognized by the People's Republic of China, where they reside in the mountainous terrain of the southwest and south. They also form one of the 54 ethnic groups officially recognized by Vietnam. In the last census, they numbered 2,637,421 in China, and roughly 470,000 in Vietnam. In Thailand they number 40,000 and in Laos 20,000.