Hardwood for cooking

Coconut husks add a very nice flavour to BBQ foods and they should be pretty easy to get hold of.

I don't have a source for you, but you might consider guava.  It is quite hard and a popular smoking wood in Hawaii.  First thing would be to track down where guava is grown in VN, probably the central highlands or the north, and seek it in those regions.  The fruit can be found in the markets so the trees must be somewhere.  Commercial culture, as opposed to backyard trees, requires pruning so there should be wood for sale.  As they are temperate region trees that require cold winters to flower, any cherry or apple woods would likely be imported from China.

Fred wrote:

Coconut husks add a very nice flavour to BBQ foods and they should be pretty easy to get hold of.

Good idea for BBQ but probably won't work for smoking as coconut is a fast burn.  I don't know where they go but I have seen bargeloads of ground husks being loaded in the Delta.  I think they may have industrial applications as polishing abrasives.

Coconut husk charcoal is very common in Indonesia so you see it being used a lot for sate and other roasted product.
It's very cheap and works very well, also adding a nice flavour to the food.