Keep a reasonable amount of cash on your person as travellers' cheques can only be exchanged at authorised foreign exchange banks, mostly in Vietnam's major cities. In Hanoi, Vietcombank at 344 Ba Trieu, HSBC at 83B Ly Thuong Kiet and ANZ Bank at 14 Le Thai To will all exchange travellers' cheques. You may be able to cash American Express travellers' cheques at Vietcombank on Hang Trong in the capital city. Most banks will charge a commission of around 2%, more or less, depending on what type of currency you are exchanging.
With the burgeoning access to ATMs in Hanoi, visitors to the capital city are carrying fewer travellers' cheques. If you plan to cash travellers' cheques at one of the authorised foreign banks in Saigon, be sure to bring your passport and any other official-looking ID. Note that Vietcombank will not levy an exchange fee on American Express travellers' cheques.