You’ve stayed for 2,5 month already and would like to stay for four months more. Personally I would at least have applied for a six months multiple entries tourist visa through the Thai embassy before I left home. Gives you 60 days each time upon arrival with a potential 30 days local extension within six months. Fee 180-200 USD.
The 90 days still runs from the day you entered Thailand last time or did your first extension of stay, unless they put a new note with a new 90 days date in your passport during your renewal.
If you don’t bring a legal IDP from home -which basically also just is a translation to the native language of all contrives who participate in the convention- some embassies offers to verify a translation of your national licence into Thai for converting.
As told several times, if you don’t have a Thai bank account you’ll need a 90 days Non O before you enter Thailand, so you basically have two options; Go back home and apply or apply through an embassy in a nearby country.