I plan on staying mostly in Bangkok when I go back, so I just need to spend some dreadfully boring hours at the immigrations office standing in line XD
The problem isn't the time after you've submitted the papers, but getting all of the right papers. And the queue for delivering the papers.
I've only ever waited like 30min max after being shuffled into the waiting-room after delivering all the papers. And that was on what I feel was busy days.