Money, currency, banks

The Thai currency is 1 Baht (THB), which is subdivided into 100 satangs.
The current exchange rate of 164 world currencies against baht can be found using this link.

Cash

Thai note 20 Bhat

  - copper coins in denominations of 25 and 50 satangs
  - silver coins in denominations of 1, 2 and 5 bahts.
10 baht coin is made of silver with copper in the middle.
Thai note 50 Bhat The notes are issued in denominations of 20, 50, 100, 500 and 1,000 bahts.

Credit cards

MasterCard, Visa, Diners Club or American Express cards are commonly accepted in more expensive hotels, restaurants and more-or-less usually in shops.

ATM

Thailand (including Koh Chang) has rather dense network of ATMs, onto busiest places the ATMs are moreover carried from time to time in a security van.
The ATMs are clearly marked as "ATM". Almost all international payment cards are accepted.