There are noted dialects of Stieng, some of which may not be mutually intelligible. However, due to the lack of widely available research, this article will primarily describe the dialect known as Bulo Stieng spoken in the provinces of Bình Phước, Lâm Đồng, Tây Ninh in southwestern Vietnam and Kratié (Snuol District) and Mondulkiri provinces in adjacent areas of eastern Cambodia. Bulo Stieng is spoken in more remote areas of the mountains and jungles alongside its close relative, Mnong. Other dialects, including Bu Dek and Bu Biek, are spoken in the lowlands and exhibit more influence from Vietnamese.
Haupers (1969) analyzes Stieng as having 25 consonant phonemes with three-way contrasts of voiced, unvoiced and pre-glottalized with aspiration described as a consonant cluster involving simple (i.e. not pre-glottalized) stops plus /h/. Analyses which include the aspirated series as independent phonemes yield 33 consonants and a five-way contrast.
Consonants appearing in syllable coda are devoiced and unreleased. For the alveolar approximate, the trilled [r] is found in free variation with the flapped [ɾ]. The voiceless palatal fricative [ç] appears only in syllable coda as a complimentary allophone of [s].
The Stieng vowel system consists of fifteen monophthongs and two diphthongs. In addition to vowel quality, quantitative length (duration) is also phonemic for vowels other than [ɛ] ([æ]) in closed syllables. The vowel [ɛ] ([æ]) is short before h and long elsewhere. This lack of minimal pairs for [ɛ] ([æ]) and [ɛː] ([æː]) suggests that [ɛ], [æ], [ɛː] and [æː] are all allophones.