Filing a case at the labour department.
You can file your complaint at the labour department without a lawyer. What you need are three things.
1. State your complaint in writing, in Thai language and as factual and as straight forward as possible.
Being factual means avoiding, among other things, the words like injustice, unreasonable, unfair, mistreatment, inhuman, violation of human rights, etc.
These words are vague and will take some length to explain thus making your complaint letter much longer than needed, and making it more difficult for the labour department to evaluate your case.
If you are filing a complaint against a school that did not pay your separation pay say it straight. For example: “I am filing a complaint against [name of the school and address]for not paying my separation pay.”