Dr Paul Neis undertook a scientific mission to Cochinchina and Laos on behalf of the French Minister of Public Education. He returned to Bangkok by way of Chiang Mai and north Thailand. His mission lasted for 19 months between 1882 and 1884.

In the central and southern mountains of Laos; Mon-Khmer tribes; known as Lao Theung or mid-slope Laotians; predominate. Other terms used for this grouping are Khmu; Khamu (Kammu) or Kha as the Lao Loum refer to them as indicating their Austroasiatic origins. However; the latter is considered pejorative; meaning 'slave'.