Until you can pay in cash you won’t get into the country and you could end up having a wonderful holiday camped on the wrong side of the barrier until your return flight leaves. If you have a bank card, an immigration officer might offer to escort you to an ATM to withdraw some money. Meanwhile you might starve to death (slight exaggeration, but you get the point) as it might be many hours before that happens. They have been known to accept payment in currencies other than US Dollars but are not obligated to do so. If they choose not to, you will have a problem if you haven’t brought US Dollars with you.
Tan Son Nhat International Airport
At Ho Chi Minh City (Tan Son Nhat International Airport) the VOA window is situated over to the left as you enter the immigration hall, at the far end. Do not join any queues for Immigration Control. The counter itself is sign-posted –  LANDING VISA.  When you get to the Landing Visa (VOA) window, be prepared to hand over your  passport, one completed copy of the Entry and Exit form, the entire letter of approval and one passport size photo (the officer will staple your photo to the form if not already attached). You should then go and sit down. Even with few people being processed do not expect passports (with the visa attached) to be returned in the order that they were presented at the window.
Landing Visa Office at Tan Son Nhat Airport
When your visa is ready, your name will be called and at the same time your passport held up to the window with the photo page showing. You then pay the processing visa fee  – U.S.$45 for single entry, 1 or 3 month. up to U.S.65$ for a One Month Multiple Entry and U.S 95$ for 3 months multiple entries . Vietnamese Dong or U.S. Dollars are the preferred currencies. The notes should be in good condition (no marks, nicks or tears) but it is not necessary for them to be brand new. At HCMC, people have also had Australian Dollars, GB Pounds and Euros accepted as payment instead of U.S. Dollars but no change is given for currencies other than U.S. dollars or Dong. However, to avoid payment problems, U.S. Dollars are preferable as there have been occasional reports of other currencies not being accepted. Once you have paid, your passport will be returned to you, along with a receipt for your payment. Be sure to check the newly issued visa for any errors while still at the window. You then go to the immigration control posts to be processed in the normal way. Baggage reclaim and Customs are downstairs.
Noi Bai International Airport
At Hanoi (Noi Bai International Airport) the procedure differs slightly. The VOA office is situated to the left as you leave the corridor and enter the immigration hall. Hand in your passport and VOA approval letter at the counter, and pick up an Entry and Exit Form if you haven’t downloaded and completed one beforehand. If necessary there are desks where you can fill in the form. Then walk along the right-hand side of the office to the counter at the opposite end and wait for your name to be called. Because foreign names can be difficult for the immigration officers to pronounce they usually also hold up the passport with the bearer’s photo facing outwards.
Landing Visa Office at Noi Bai Airport
When you have handed your payment completed Entry and Exit form and passport photo to the immigration officer he or she will give you a receipt and return your passport to you, complete with the visa stamp. Check that the exit date on the visa is correct (that is, in one month’s or three months’ time), then retrace your steps along the side of the office and proceed to Immigration Control. Turn right for baggage reclaim and Customs.
Da Nang Airport
At Da Nang Airport follow the exit signs. As soon as you enter the huge hall it is very easy to find the VOA window – it is on the left hand side and is clearly visible. The process is reasonably quick (approximately 15 minutes with all necessary paperwork completed before landing) but do bear in mind there is no guarantee it will be always be the same. After receiving visas / passports back, progress onwards to immigration control. Immigration Control can be slow, sometimes 3 or 4 long lines. Everyone queues up together going through the same check-points and there are no separate checkpoints for Vietnamese passengers and other nationalities.
Tip:Â If there are two or more of you obtaining VOA it would be prudent that once you’ve handed in your paperwork, that one of you stands in line for immigration control. That way you won’t be at the back of a long queue.
For your convenience, you should take a look for the airport map before landing to save your time at the airport:
Noi Bai International Airport Map
Noi Bai International Airport Map