Currently on ARC - want to get student visa

I am currently contracted by a bushian that provided me with my ARC. My contract at my bushiban expires end of Feb and my ARC end of March. My problem is this - I am starting at an elementary school on 14 Feb - before my contract at bushiban expires. I am going to Thailand for CNY, and would like to arrange my student visa while I am there. If my student visa (on which I will be working at the elementary school) then replaces my ARC, I will be working at my bushiban for approximately 2 weeks without an ARC, and without them knowing that I do not have an ARC.
What are the implications?
Also - what documentation do I require to get a student visa?

That’s a bizarre post. Who told you you can work on a visitor visa (for the purpose of studying)? If the school can’t get your work permit in time you will have to leave, otherwise not. If the school won’t get a permit for you, obviously you’re gonna be working illegally. Two weeks is sufficient to get the work permit and ARC, so what’s this new ‘school’ doing about it?