The Northern Thai language or Kham Mueang (Thai: คำเมือง , Lanna: ) or Lanna is the language of the Thai Yuan people of Lannathai, Thailand. It is a Tai language, closely related to Thai and Lao. Northern Thai has approximately six million speakers, most of whom live in Thailand, with a few thousand in northwestern Laos.

Speakers of this language generally consider the name Yuan to be pejorative. They generally call themselves Khon Muang (คนเมือง) (or Lannathai or Northern Thai). The language is generally known by one of these terms, or as Phayap. The term Yuan is still used for the distinctive Lannathai script, which is closely related to the old Tai Lue Script and the Lao religious alphabets. It also resembles the Burmese and Mon alphabets. (All these alphabets derive from the Old Mon alphabet.) The use of the tua mueang, as the traditional alphabet is known, is now largely limited to Buddhist temples, where many old sermon manuscripts are still in active use. There is no active production of literature in the traditional alphabet.

Most linguists consider Northern Thai to be more closely related to Thai and the other Chiang Saeng languages than to Lao and the Lao-Phutai languages, but the distinction is never easy to make, as the languages form a continuum with few sharp dividing lines.

Pronouns

Pronouns may be omitted once they have already been established in the first sentence, unless the pronoun in the following sentences is different from the first sentence. The pronoun "you" may also be omitted if the speaker is speaking directly to a second person. Moreover, names may replace pronouns, and they can even replace the first person singular pronoun.

Phonology

Lanna phonology is relatively closer to Lao phonology because of the sound.

Vocabulary

Lanna shares many vocabulary with Standard Thai especially scientific terms(of which themselves draw many prefixes and suffixes from Sanskrit and Pali), and it also has its own distintive words. And just like Thai and Lao, Lanna has borrowed many Sanskrit and Pali words.

Different words

Many words differ from Standard Thai greatly:

• ยี่สิบ > ซาว (/jiː sib/ > /saːw/, twenty)

• พูด > อู้ (/pʰuːt/ > /uː/, to speak)

• พี่ชาย > อ้าย (/pʰiː tɕʰaːj/> /ʔaːj/, older brother)

Similar words

Some words differ in tone only:

• หนึ่ง > นึ่ง (/nɯŋ/, one)

• หก > ฮก (/hog/, six)

• เจ็ด > เจ๋ด (/tɕet/, seven)

• สิบ > ซิบ (/sib/, ten)

• เป็น > เป๋น (/pen/, to be)

• กิน > กิ๋น (/gin/, to eat)

Some words differ in a single sound and associated tone. In many words, the initial ร (/r/) is spoken as ฮ (/h/):

• ร้อน > ฮ้อน (/rɔn/ > /hɔn/, hot)

• รัก > ฮัก (/rag/ > /hag/, to love)

• รู้ > ฮู้ (/ruː/ > /huː/, to know)

Many aspirated consonants often become unaspirated:

• เชียงราย > เจียงฮาย (/tɕʰiaŋ raːi/ > /tɕiaŋ haːi/, Chiang Rai city and province)

• คิด > กึ๊ด (/kʰid/ > /gid/, to think)

• ช้อน > จ๊อน (/tɕʰɔn/ > /tɕɔn/, spoon)

• ใช้ > ใจ๊ (/tɕʰai/ > /tɕai/, to use)

• พ่อ > ป้อ (/pʰɔ/ > /pɔ/, father)

• ทาง > ตาง (/tʰaːŋ/ > /taːŋ/, way)

Though many aspirated consonants often become unaspirated, when a unaspirated consonant is followed by ร (/r/) the unaspirated consonant becomes aspirated:

• โกรธ > โขด (/groːt/ > /kʰoːt/, (be) angry)

• ประเทศ> ผะเตด (/praʔtʰeːt/ > /pʰaʔteːt/, country)

• กราบ> ขาบ (/graːb/ > /kʰaːb/, to prostrate oneself)

Other differences:

• ให้ > หื้อ (/hai/ > /hɯ/, to give, let)