There are several international banks available in the larger Cambodian cities.  ANZ Royal offers the most locations, educated staff and modern equipment.

You can handle most of your international banking needs in Phnom Penh, Siem Reap and in Sihanoukville. 

  ATM's

There are a plenty of ATM's in Phnom Penh, Siem Reap and Sihanoukville.  

credit cards 

Do not plan on your credit card being your main source for spending money in Cambodia.

Only the finer locations will accept Visa and Master Card.

Better to bring travelers checks, and an ATM card or two.

currency - khmer riel

Cash is the main way to make purchases throughout Cambodia.  

While the US dollar is the currency used for nearly all large purchases, small expenditures are often handled using the Khmer Riel.

The exchange rate is approximately 4,000 Riel to $1.00.

Currency exchanges abound throughout Cambodia.