If the local jurisdiction says it isn't theft then it isn't theft. I don't know about Vietnams legal system you understand, but I have to say that I remain deeply suspicious about attempts to enforce western legalities the world over.
I can see that you could sleep quite easily as an author or inventor knowing that is certain poorer parts of the world your property rights don't enjpy the same protection as they do in the west.
(There might be some concerns over offshore duplicates being re-imported into the west, but then that is what treaties are for: "You want to trade with us, you do it our way." There is nothing wrong with that, and I for one would see it as a far better use of sanctions than some others that we've indulged in.)
OTOH, if the local law says it *is* theft, then maybe the problems that keep such countries poor are not unrelated to the lack of a credible legal system that protects the rights of all.