Transcribe a Romanized Lao syllable in the region FROM and TO to Lao string.
Only the first syllable is transcribed.
The value has the form: (START END LAO-STRING), where
START and END are the beginning and end positions of the Roman Lao syllable,
LAO-STRING is the Lao character transcription of it.
Optional 3rd arg STR, if non-nil, is a string to search for Roman Lao
syllable. In that case, FROM and TO are indexes to STR. (fn FROM TO &optional STR)