The farang teacher in my local school had the school install air conditoning in his room before he would commit to start work.
I suspect that basically came down to the law of supply and demand.
If there are a lot of falangs available - or perceived to be available - the teacher can not negotiate terms and conditions. They are written in stone.
In the school I'm at - I haven't seen or heard an air conditioner in operation anyplace. Haven't found out where the director's office is yet - but that would probably be the only place that there is one.