There are places that you can exchange your money:
Banks: Most banks in Vietnam have currency exchange services. There are Vietcombank, Vietinbank, Agribank, Eximbank, etc that you can freely choose as they are all high quality banks in Vietnam. There’s a commission rate of 0.5% – 2% when using the services.
Hotels: Big hotels also have services for foreigners to exchange currency. Small hotels may charge you a service fee.
Airports: There are stalls at the airports for currency exchange services. However, the exchange rate is not that good for foreigners. I’d suggest exchanging for a small amount to cover your taxi expenses. After that, you can use exchange services in town for a better exchange rate.
Gold and jewelry shops: Gold and jewelry shops are known to have the best exchange rate compared to banks, airports, and hotels.
It’s recommended that you ask for advice from those who have been to Vietnam before for better preferences.