It is usually classified as a Khmuic language, a subgroup of the Austroasiatic languages. LinguistJørgen Rischel has studied the language and described its peculiarities in several works. He divides the language into three varieties: one spoken by a small group in Laos and previously called Yumbri, and two others spoken by larger groups in Thailand. They differ in intonation and in lexicon.
Although it is possible to count up to ten in Mlabri, only the numerals one and two may be used to modify a noun, and the word for 'two' has uses closer to 'pair' or 'couple' in English than a numeral.
Mlabri distinguishes rounding in its back vowels. It does not have the register systems of some other Austroasiatic languages.
All vowels occur long and short. /a/ is fronted after palato-alveolar consonants, and may approach [ɛ]. There is also a very short vowel /ɪ/ that has limited distribution. Schwas occur in pre-tonic syllables, but may be epenthetic. There are several diphthongs.
Consonants include glottalized plosives and partially voiceless sonorants.
Mlabri has a different set of consonants which occur at the ends of syllables, including aspirated sonorants /lʰ, rʰ, jʰ/.[are these voiceless or murmured?] The second is a trill, and the third more post-alveolar than palatal. Other final consonants are /p t c k ʔ m n ɲ ŋ h l r j w/