@Adam *******
you'll know how good the plan is when you get the under consideration stamp and see when you need to return to the immigration office. IF it's not by the time you get back to thailand, you need to tell them RIGHT THEN AND THERE and you need to show them your airfare out and back.
I have seen them adjust the under consideration stamp to allow for out of country travel before. (remember that 30 days is actually the first month of your next year extension)