@Rob ********
dial back the paranoia just a notch or three, IF you have a multi entry visa <- which with a DTV you have one for FIVE years, just because you weren't able to meet the requirements for an in country extension doesn't invalidate the VISA.
You could still bounce out and back and get a new 180 day entry stamp,
AND
if you ran on overstay before you bounced out and back you would pay 500baht a day like everyone who overstays their stamp