Hi nyc0301,
The unit of currency in Vietnam is the Dong, however the US Dollar is the most favoured foreign currency. When you exchange your money you’ll need to produce a copy of your passport so it’s important to bring a photocopy of your passport with you. Once your money has been exchanged you’ll receive a receipt. Keep this with you in case you need to change money back before you leave any of the countries.
The unit of currency in Cambodia is the Riel. Again, we recommend that you take your spending money in US Dollars cash in small denominations. Please do not change your US Dollars in to local Currency, as Cambodia is primarily a cash based economy
Please note that banks will only accept notes in perfect condition. The smallest tear or defacement will result in your cash being refused. UK visitors should note that Scottish or Northern Ireland bank notes are NOT accepted.
I hope this helps.
Kindest Regards,
Monty