It’s because it’s a socialist territory, where most large businesses are owned by the government, or insiders, and receive subsidies and protection from competition.

If there’s just one or two employers in a sector, and impossible for competitors to start up without government connections, employers can set very low wages, which keeps critical costs , such as labour, very low, but allow for reasonable profits for “the owners”.

Mix with a large, incredibly poor, relatively young population, and voila!

There’s illusion of competition. Telecom is the best example i saw there - Viettel(military), Mobifone (Vietnam government Post / Telecom)

Also, they have high protective tariffs and sales taxes on many products.
Try to buy a motorcycle over 250cc, especially a Harley Davidson, BMW, a large Honda.
See if you think that’s cheap, after a 100% tax.

Much of the subsidies, as usual, come from the inflation tax, which you don’t notice, if you have harder foreign currency. That’s how everyone there became a millionaire in VND.

Energy sector is completely controlled by SOEs, and so on…