Brunei Malay is characterised by just three vowels, /i,a,u/, in contrast with the six vowels of Standard Malay, /i,e,a,o,u,ə/. In particular, note that the last of these, /ə/ is absent from Brunei Malay. As a result, it should be possible to represent Brunei Malay words using three vowel letters, and 'e' and 'o' should be redundant. However, look at the entry for buat:
Note that both berbuat and membuat use the letter 'e'.An alternative representation of berbuat for Brunei Malay would be babuat. However, just as with aku and saya, the dictionary compilers seem to be de-emphasising the differences between Brunei Malay and Standard Malay.
Younger speakers of Brunei Malay might object that they don't say this word with a fully open [a] vowel in the first syllable. But this could be handled by means of phonology: we could represent the word as babuat and state that /a/ is pronounced with a central allophone close to [ə] when it occurs in a verbal prefix. In other words, there are just three vowel phonemes, /i,a,u/, but they get pronounced in various ways according to the phonological environment.
