I learned (probably incorrectly) that most teachers did not learn to use "any" dictionary.

Thai dictionaries have other peculiarities. The words are not arranged "logically" but arranged by "physical alphabet encoding" (ask any Thai programmer to explain how to "sort" Thai words -- if you can understand their answers, you would know how to look up Thai words in Thai dictionaries.)

I use Stardict look-up program on a computer because I can't remember Thai alphabet physical sequences and I can't read small prints on dictionary books easily anymore ;-)