How long do you have to submit your financials for bank certification for a Thai visa application?

You don't submit any financials to the bank. If you are using 100% banked money method (800K baht) you go in and they write a letter stating your name, passport number, account number and bank balance on the date they wrote the letter. It's just a few lines.

I'm not sure what you're asking :/ Most (as in more than a few) immigration offices allow the bank letter to be no more than 7 days old, BUT some want it the same day or not more than a day or two before.

I'd say call or go to your immigration office and ask them.

Bangkok will let the letter be up to 7 days old as long as you update your bank book on the date you're applying for an extension