The Tai Dam language is similar to Thai and Lao, but it is not close enough to be readily understood by most Thai and Lao speakers. In particular, the Pali and Sanscrit additions to Thai and Lao are largely missing from Tai Dam.
Tai Dam speakers in China are classified as part of the Dai nationality along with almost all the other Tai peoples. But in Vietnam they are given their own nationality (with the White Tai) where they are classified (confusingly for English speakers) as the Thái nationality (meaning Tai people).
The Tai Dam language has its own system of writing, called Tai Viet, which consists of 31 consonants and 14 vowels. Although the language is tonal, there are no tone markers, as there are in Tai and Lao. According to Thai authors, the writing system is probably derived from the old Thai writing of the kingdom of Sukhotai.
An effort is underway to standardize the script in Unicode:
At the Workshop on Encoding and Digitizing the Thai Script, held on November 3, 2006 in Điện Biên Phủ, Vietnam, it has been proposed that the name of the script be called Tay, to indicate the Tai language as spoken in Vietnam.
At a Unicode subcommittee meeting on February 6, 2007, a proposal on the Tai Viet script was submitted by James Brase of SIL International.
At the ISO/IEC JTC1/SC2/WG2 meeting on April 24, 2007, a revised proposal for the script, now known as Tai Viet, was accepted "as is", with support from TCVN, the Vietnam Quality & Standards Centre.
The Tai Viet script is present in Unicode as of version 5.2, in block Tai Viet U+AA80..U+AADF, and in ISO/IEC 10646, in parallel.