If it is Hua Hin main Immigration.. next day is perfectly OK... I have been going the 'next' day for the past 4 years.. but please feel free to do it all on the same day :)
You can go to Kasikorn on the Wednesday.. get your bank statements and bankbook updated before you go Immigration the next day (Thursday). I have always gone the day after Bank updates to Immigration.. not a problem. ps. I am in Hua Hin.
An option is to stay at a cheap Hotel for 1 night (in Nonthaburi) where they will submit the TM30.. you then ask for a copy of that TM30 and go back to your Nonthaburi Immigration. Should be no need to go back to Bangkok.
you sound like a cheap charlie (or charline)... the DTV encourages low-lifes to enter Thai for possibly 5 years.... do your 'cooking' class in the States!