I doubt they are mostly foreign accounts.

It’s not easy to open a bank account in Vietnam even before these changes. Typically you’d need some sort of long-term visa.

It’s more likely Vietnam who opened these accounts. Often done to keep money of dubious sources separate from their normal bank account.

Hiding money from the tax man is incredibly common in Vietnam. It’s very common for businesses to pay themselves some small amount, declare it on taxes, then take the other 80% of income tax free.

Not to mention the extensive bribery in Vietnam.

> Typically you’d need some sort of long-term visa.

You only need a six month visa so it's not that bad. You need a year visa to get a bank card though, but that's not such a big deal since everywhere uses QR code payments here, and you can even withdraw cash from ATMs using the app. I only ever use my Vietnamese bank card for Spotify since that gets me a nice discount.

The big problem is that, whatever type of visa you have, if it expires for some reason then your account gets locked. Hasn't happened to me so I don't know how quick/strict they are. But the rules are changing so quickly here - both for visas and for banking - that I don't feel secure keeping any amount of money beyond my daily needs in my Vietnamese bank.

I visited as a tourist/backapcker ~10 years ago, with visa on arrival. Opened a bank account by walking into a bank with my passport, and walking out 10 minutes later holding a fresh new debit card. It was the easiest of any country I've ever visited.