I taught in China for 10 years -- 3 different schools. One was ok (stayed there 2 years), one was great (stayed there 7 years) and one was awful.
Usually in China, we'd know if a school was good to work for or not by word of mouth among local expats (of course, there weren't a whole lot of us so we all knew each other), and by consulting previous teachers via email or phone. And there was a website that posted objective reviews.
Is that sort of thing generally done in Thailand? I know you can't post negative stuff about schools on this site, but what about positive -- like "so & so at such and such school really knows his/her stuff about how to get all the right documents for FTs so they can get their Non-Imm B visa before their 30 days runs out."
I'm just concerned about walking into some dreadful situation -- admin not knowing how to process documents, consistently getting paid late, that sort of thing -- and you can't really find that info out until you work there, unless there's some sort of communication among the FTs.
You could always try posting in the 'Schooltalk' section of the Staffroom. That way you could also find out who you could exchange private messages with. There was a website dedicated to this, but it was closed for legal reasons.
Short answer = ASK.
Longer answer = ...
If you are there and interviewing in person, take a few minutes and talk to some of the staff when the boss isn't looking (lunchtime?).
If you are abroad and interviewing ask for the contact information of some of the staff (current or former) and ask them when the boss isn't reading/listening over their shoulder.