Phasa Muang (Thai: ภาศาเมือง), or Kammuang is the modern spoken form of the old Northern Thai language that was the language of the kingdom of Lanna. Central Thai may call northern Thai people and their language Thai Yuan. However, "Yuan" is their word for Vietnamese people; in everyday speech, "Tai" prefixed to some location is understood as meaning "Tai person" of that place. They call their language Kammuang, in which Kam means language or word; muang; town, hence the meaning of "town language," specifically in contrast to those of the many hill tribe peoples in the surrounding mountainous areas.
The Tai Tham alphabet formerly in use by northern Thai people is also called Lanna script. Due to the effects of Thaification in the wake of Monthon reforms, few northern Thai can read or write it, as it no longer represents accurately the orthography of the spoken form.
^Raendchen, Jana (October 10, 2005). "The socio-political and administrative organisation of müang in the light of Lao historical manuscripts" (PDF 316 KB). In paper 31. The Literary Heritage of Laos: Preservation, Dissemination and Research Perspectives, Vientiane: National Library of Laos. The Literary Heritage of Laos Conference, 2005. Website content written by Harald Hundius and David Wharton, Lao translation by Oudomphone Bounyavong, edited by Harald Hundius. Staatsbibliothek zu Berlin Preußischer Kulturbesitz: Digital Library of Lao Manuscripts. image 4, page 404. Retrieved September 12, 2013. "Traditionally, these people called themselves according to the place of their settlement, combining the term “Tai” (man) with the place name, as for example Tai Müang Phuan, Tai Müang Swa (Luang Phabang)."