Khmer ios spoken in Mekong Delta of Southwesten
Vietnamand also in Kampuchean and Thailand.
Khmer syllables are assigned to one of two
'registers'. Vowel qualities often differ between
registers with some being limited to one or the other. In
careful speech lower pitch and breathy phonation
distinguish second from first register, but often only
vowel differences remain in more rapid speech. In
addition to the short diphthongs listed there are a number
of vowel sequences.

Ehrman, M.E. and Sos, K. 1972. Contemporary Cambodian.
Foreign Service Institute: Basic Course Series.

Huffman, F.E. 1970a. The Cambodian System of Writing and
Beginning Reading. Yale University Press, New Haven.

Huffman, F.E. 1970b. Modern Spoken Cambodian. Yale
University Press, New Haven.

Jacob, J.M. 1968. Introduction to Cambodian. Oxford
University Press, London.