Baan Aksorn is definitely up there near the "top of the heap" as far as private Thai language schools go.

They have a wide variety of levels and programs you can take. It doesn’t matter if your main goal is strictly conversational Thai, reading & writing, or a combination of all of 'em. They have very qualified teachers who have plenty of experience teaching Thai to foreigners (Something which is a MUST for foreigners to learn this language!)
I give them a "very good" rating in terms of "bang-4-the-baht". That's a term I coined to mean "what you receive in instruction in relation to what you pay in tuition".

..
I dunno about finding a Thai language teacher from any regular Thai school and getting any measurable results from it (other than helping offset the abysmally low pay scale they're on

).
I've sat many Thai language grade school classes both up-country and in Bangkok. Given almost EVERY subject is taught here "by rote learning", I honestly doubt your 'run-o-the-mill' Thai language teacher would have the necessary skill-set to even be qualified enough to teach Thai to a non-native speaker. They are not used to being questioned about the "whyz-in-thai", or why something is done in Thai differently from English. In fact most of the classes I sat didn't even have a question and answer period after the lessons were taught. Also remember even in the kindergarten Thai language classes
ALL the students ALREADY speak Thai far better than foreigners who’re just starting out.
I think you're far better looking in the private Thai language school sector for a school which fits your needs as far as what you want to learn and meshes with how you learn things too.

"Whoever said `Money can`t buy you love or joy` obviously was not making enough money." <- quote by Gene $immon$ of the rock group KISS