I did a major Overland trip, including Vietnam, Cambodia, Myanmar, Thailand, etc. and found my prepay card invaluable. Works for getting cash at atms with a far better rate than my bank, and all controllable from my phone. I took to on the same account, with one of them hidden away in my backpack, frozen and unusable unless I reactivated it. And a spare SIM card. I used Revolut, though there are others. I deactivated it between uses. Oh, and I got a message on my phone every time I used it. Brilliant device. Rechargeable via my bank or a debit card, and swap between major currencies.