Hi Gilliano,
When travelling to Thailand we would advise that you take a mix of cash and cards with you. Foreign currencies can be exchanged at banks, hotels and, in larger towns, the Bureaux de Change. It is worth mentioning that outside the larger towns and tourist areas notes higher than 500 Baht may be difficult to exchange so it would be worth carrying small change. Credit cards are widely accepted and there are ATMs in all major cities. Should you wish to take Travellers cheques, these are accepted by many banks and large hotels.
Kind regards
Julia, your editor