I just read this article -
http://www.smartertravel.com/blogs/t...ml?id=10720015 - and one of the things it said was:
And finally, in much of the world, especially Asia, Europe, and the South Pacific, independent, low-fare airlines can now often undercut airpass prices and provide point-to-point flights at substantially lower prices than even the "discount" prices on the visitor coupons.
You're probably better off going directly to the Vietnam Airlines website to price out the flights you want, or checking out the discount carriers that operate there (AirAsia, Jetstar Asia).