I know many UK based visitors to Thailand use Nationwide Visa and Debit cards because up to now they haven't charged fees. Sadly, this is about to change. Their website has the following notice:

"When you use a Nationwide Visa debit card or credit card to make a transaction in certain currencies other than sterling, Visa charge a fee for each transaction and Nationwide currently pays that fee on your behalf.

We will start to pass this fee onto you from 6 May 2009 on credit card and from 1 June 2009 on debit card and it will be included in the sterling amount shown on your statement.

The fee is currently 0.84%. From 1 July 2009 this fee will increase to 1%."
Anybody know any other methods of avoiding transaction fees when using Visa, or Visa Debit, cards in Thailand?