Question:
The biggest sources of income for Vietnam probably include the following:- Export of oil and natural gas.- Export of agricultural products like rice and rubber.- Export of mineral ores etc. from mines.- Assembly works for foreign companies.

Vietnam has a lot of oil and natural gas reserves , which may be extractedand sold for foreign currency.

Assembly works for foreign companies inside Vietnam is probably among thebiggest sources of income. Vietnamese labor is cheap. All they need isskills and discipline.

Answer: Probably, except mineral oresYou know the phrase "cheaper than dirt", meaning ain't worth much.Let me tell you some ores are cheaper than dirt, just like gasolineis cheaper than drinking water (ref. vosanluumanh)

There is a catch though. A parcel of 500K barrel of oil can besold with the press of a computer button, for $10mil USD. The samevolume of drinking water is worth 10 times more (at $1.20/litre= $100mil USD) but will take many hundred man-years to sell. ForHyena's pleasure I will add many hundred woman-years as well :)

So being cheaper than dirt/water, the only way to make money isby moving huge volume. Even assuming VN has the minerals, the sizeof the deposits cannot support the scale of operations that is ofinterest to multi-national companies. And that's not yet talkingabout the lack of infrastructure support and the nationalistic(but naive) attitude of VN govt officials that these companiesmust come and "beg" for the rights to excavate the ores.

The outcome of all above was my ex-company took their investmentmoney and went dig somewhere else.