Just finished a 2-week trip in Vietnam and used only my Monzo card to survive - here’s some tips:
Most places don’t take card (debit or credit), so you’ll need to withdraw cash to pay for most things. For larger shops or local travel agencies (eg for tours) that take card, typically a 3-5% card surcharge applies, so you’ll have to weigh up the convenience versus paying the surcharge
Most ATMs have withdrawal limits - some with ridiculously low limits (eg. 2 million VND or ~£70) - and most ATMs also charge withdrawal fees for foreign cards (ie. the bank that owns the ATM charges you, not Monzo). Some charges a flat 3% of any amount (eg. Techcombank) but some charges a flat rate (generally 20,000 VND to 50,000 VND) no matter how much you withdraw up to the withdrawal limit. Beware as the transaction fee is sometimes not disclosed (depending on the bank) but the bigger banks generally will warn you how much the fee is before you decide whether you want to go ahead.
Thanks to tips in this thread, I only used (a) VP Bank (b) Military Bank (MB) and © SeABank - all three don’t charge any ATM withdrawal fees and all have reasonable withdrawal limits. All 3 banks also stock small denomination notes (as low as 10,000 VND notes), so don’t worry about punching in weird withdrawal amounts just so that you can have some small denomination notes. Here’s how to find them in most of the tourist places:
(a) Hanoi - if you fly into international terminal of Hanoi airport, there’s a VP Bank ATM on arrival floor. Once you exit from customs, turn right and walk to the end of the building and you’ll find it. Very handy as I withdrew a combination of small notes to pay for arrival shuttle buses to the city. In Hanoi itself, VP Bank, Military Bank and SeABank ATMs are everywhere and I found that Google Maps tag them pretty well, so just do a search
(b) Halong Bay - withdraw all the cash you need before you hop on the bus to the marina! The marina recently relocated to another part of town (to accommodate for sheer increase in number of tourists) and the new marina doesn’t seem to have great facilities yet, other than small souvenir shops and cafes.
© Hue - VP Bank, MB and SeABank were all hard to find, so stock up on cash before you get there!
(d) Hoi An - I found that MB was the most convenient and has an ATM a few minutes walk from the Old Town. VP Bank and SeABank are in Da Nang (30 kms away) but don’t seem to have local ATMs in Hoi An. Google Maps have MB’s ATMs well tagged.
(e) Ho Chi Minh City - Same as Hanoi - VP, MB and SeABank are all everywhere and easy to find. Ho Chi Minh City airport also have good choices of ATMs in both the international and domestic terminals, so just use one of the 3 banks. (All the ATMs are next to each other).
Not related to money matters but beware of “fake taxis” that are painted exactly like VinaSun taxis in HCMC. If possible, get your restaurant or hotel to order a taxi for you, as opposed to getting one off the street. If you have to get one off the street, take care to match the phone number on the taxi itself to the real phone number of the taxi company before you get in.