The Muong speak a Mon-Khmer language which is linguistically related to Vietnamese.

Han (classical Chinese) was the official written language of Vietnam during the 1,000 years of Chinese rule. During this time, however, the spoken language continued to develop. The city dialect became the common Viet language, but the mountain dialect developed into the present Muong language. The Viets recovered their independence and established the nation of Dai Viet in the l0th century. By this time, the linguistic split between Viet and Muong was complete.

      Muong is an Austro-Asiatic, Mon-Khmer Language.   It is classed as part of the Viet-Muong branch.  Ropal code for the Muong language: MTQ00l