Drum Publications has written a guide on how to the pronounce the Karen alphabet.
Phonetics is always at the top of the list for teaching language. The references below may be useful to you.
The Karen alphabet (using Burmese script), and spelling of words was developed in the early 1860s by English missionaries. Since each vowel and consonant sound has one, and only one symbol, it makes an excellent phonetic transcription tool for teaching adult Karen students the sounds of English letters.