There is no charge for transfer of stamps to new passport. If you get asked then ask for a receipt. They won't give you one. So don't pay. I've renewed my passport twice since living here. First time was when the officer told me of 'no charge'. Second time an officer asked for 4-500 baht. I refused to pay. No problem, got my stamps transferred and off on my merry way. Buriram is my office.