Is there a rule that governs the second tone in the words ประโยชน์ and ตำรวจ (low tone versus what I would think would be a falling tone), or they just rare exceptions to the rule?

I think I fatfingered my first attempt to post this question.....sorry about that

Edited November 18, 200817 yr by kokesaat

In Thai there are a few words that have mismatches between spelling and normal pronunciation.

เขา (he, she, they) is often pronounced เค้า

ฉัน (I) is often pronounced ชั้น

ประโยชน์ (advantage) is often pronounced ประโหยด

ประโยค (sentence) is often pronounced ประโหยก

There are more.

Now with ตำรวจ... I was just about to try and explain it when I came across this excellent link.

EDIT: Having read through the thread I linked to, I think Rikker may be able to shed some more light on the words ประโยชน์ ประโยค and another one ประวัติ (history) and the reason why the second syllable is pronounced with a low tone rather than a falling tone.

Edited November 18, 200817 yr by 5tash

... and here's a reference for Non-conforming Initial Clusters, where ประโยชน์ , ประโยค , ประมาท , and ประวัติ are specifically noted. Thanks David.