What should I do if my education visa application in Thailand is denied and how does my current visa extension affect this situation?

I am currently in the kingdom on a visa:

type 'Tourist', category: 'TR', no. of entry 'S',

that was used September 15 and "admitted" November 13.

I also have a 30 day extension, which I got this morning, which is until December 13.

I have signed up for a one year Thai language school and all of the paperwork for applying for an education visa seems ready.

I have a two way plane ticket to Hanoi, for applying for the education visa. Departure November 12 (one day before the original visa term ends) and return November 16 (after the original visa term ends).

My reason for getting this extension is for the case that my application for an education visa get denied. Then, I would have time to apply in a different embassy or for some other type of visa, like volunteering.

What I have realized on my way back from the immigration office is that this extension that I just got might not be relevant any more once I exit the kingdom.

Please shed some light on my situation and especially how I should prepare for the case that my application for an education visa is rejected.