Most teachers are working in Thailand illegally. The reason for this is simple - most agents or schools don't provide costly work permits. A school justifies it by saying an agent should provide the work permit and the agent justifies it by saying the school should provide the work permit . Meanwhile it is the foreign teacher at risk. Does the school or agent care? Actually schools and agents are hoping a teacher lasts only one year because they can have a fresh face the following year. Besides having a teacher with years of experience is not important but having a handsome or beautiful teacher is because of selfies.
One more thing, Thai teachers usually give "the foreigner" all the shifts they themselves don't want during the day. That's why the newcomer usually works the early morning and late afternoon classes. My advice is to smile more and say yes to everyone. Be humble and do other people's jobs. Be thankful you get to work with people who smile at you but dislike all foreigners. If you understand the Thai language, laugh as much as you can when you are the butt of most jokes. And remember if you don't like it you can always go back home. There will be another young newbie to take your place.