Legal Resignation Period for School

I have a two year written contract in the English language with my international school that states I must tell them the first week of semester two (January) if I want to leave at the end of the academic year (end of June)...At the time of signing, I didn't think I would be leaving anytime soon and naively ignored questioning the long resignation period. However, now wanting to resign and leave at the end of the academic year, I find myself in the predicament of it being May already and wanting to resign.

I've been told that the official Thai labour law requirement is 30 days and an employee must be paid up until their last working day as long as they give notice in writing 30 days minimum...which is why I want to know what legal position I'm in if they try not to pay me for my last month at the school due to 'not giving enough notice that the contract states' ? 

In the contract, it states that if I don't give notice that the contract requires, the school will take what is owed for damages out of the salary...

It's also worth mentioning that no probation period is mentioned in the contract and they paid for my work permit and non-b visa, which runs out at the end of June.

Edited May 5, 20188 yr by 90ev24