Lefèvre-Pontalis (1892)[1] reports the presence of Asong in Poufang,
Lai Chau province,
Vietnam, and provides a word list for Asong as well.
References
^Lefèvre-Pontalis, Pierre. 1892. Notes sur quelques populations du nord de l'Indo-Chine [Notes on some populations of northern Indo-China]. Journal Asiatique 19, 8, 8. 237-269, 129-154, 291-303.
You Weiqiong [尤伟琼]. 2013. Classifying ethnic groups of Yunnan [云南民族识别研究]. Beijing: Nationalities Press [民族出版社].