I have accounts with about every bank in Thailand for years already. In the beginning Bangkok Bank, SCB,CIMB and krungsri would not deduct withholding tax. UOB, Kasikorn, LH Bank and TTB always deducted withholding taxes. After a few years that changed, because they say they were informed by the Thai revenue department that the total of my interests would exceed 20.000 baht. Now they all deduct the withholding tax, and at the start of the new year I get my documents from each bank, and claim it all back from the revenue department