The labor law in Thailand is NOT gray
Postbox letter from Jonathan
There is no gray area here. Always go with a Thai. Always speak to a supervisor if anyone tries to fob you off with the 'this doesn't apply to you' crap. Nearly all schools will settle at the initial arbitration meeting.
Go to labor court
Postbox letter from Kru Anon
The labor court can be your best friend if you think you are being unfairly dismissed from your teaching job.