There is no shortage of ATMs on Koh Samui that will accept international bank cards. Be aware that almost all Thai ATMs impose a 150 Baht fee (around $5 USD) for each international withdrawal for the machine, regardless of the amount. Therefore you should try to take out the maximum 20,000 Baht each time you use an ATM to get full “value” for the fee.
It is a good idea to bring cash in a major currency (USD, Euros, Pounds Sterling, etc) as a backup to exchange if for any reason your ATM card is declined or lost. Traveller’s cheques are another alternative as a backup plan.
Don’t bother purchasing Thai Baht before you leave your home country – you will always get much better rates exchanging foreign currency within Thailand itself. The exchange rate you get at a Thai ATM is competitive, but obviously the $5 fee doesn’t help.
Credit Card Security
It’s more likely you will lose your credit cards than actually have them stolen while travelling, but it pays to be prepared. Be sure to take photos with your cameraphone of the front and back of all your credit cards and store the photos in your email account. That way if you lose them you have the complete details of the cards available. Make a note of the number to call to cancel each card. 5 minutes doing this once can save you endless grief later.
Official Thai Bank Rates
This website shows the major Thai banks and the current exchange rates they offer (updated daily). Bangkok Bank is probably has the best exchange rate of all the major banks.