ZBedic is a excellent dictionary program; it supports dictionary sorting using a.) user defined character precedence and b.) Unicode character position (codepoint ? Is that the right terminology ?)
Anyway, these mechanisms are insufficient for displaying and using a Thai dictionary in the correct sort order. As you enter a word, ZBedic shows a list of words on the left side of the screen but the order is wrong so you cannot see relevant similar words as you would expect to see in a printed dictionary.
I have patched ZBedic to support Thai sort order. If a Thai word is detected then the strings used in the comparison are preprocessed. This means that my patched ZBedic can also be used with dictionary files in other languages with no change.
You will need Thai dictionary files sorted using mkbedic built from my patches and a special build of ZBedic, all available from http://www.lyndonhill.com/Projects/zbedic-thaisort.html
Let me know if you need any help.