If you use Agoda (a hotel booking site). Book your accommodation for the duration But use the pay at reception provision. If you don't want to stay at that particular accommodation for the whole six months you can always cancel it 3 days before at no cost to you. Beaware to have separate booking as once you acctivate that accommodation booking you may have to pay for it all.
thanks Tod.. its not so much the the money side of things its about 10km to the border or a 45 km to Surin (if surin has a office) or 85 km Buriram (no taxi service in Sangkha)
l was a day late once miscounted my days l was ushered to another desk at passport control no stamp no fine just told me to count arrival day as day 1. Good luck.