“You may be better off paying cash than using a credit card. While it’s technically against the law for the Thai vendor to pass onto you the fee that the credit card company charges them (approximately 2.25% to 3.5%, depending upon card type), it’s quite common for them to do so, and it’s usually not negotiable — you either pay the surcharge or don’t use your credit card. They often want to charge 4 or 5% instead of the 2.25% to 3.5%.
You should also be aware that many vendors use a third party to bill your credit card. So they may be paying the fee to the 3rd party.
If you lose your credit card or have other problems, you can reach the credit card companies in Bangkok on the following numbers.
MasterCard (02) 260-8572
Visa (02) 273-1199 or (02) 273-7449
American Express (02) 273-0022 or (02) 273-0044
Diner’s Club (02) 238-3660