The original post was made back in 2013 so this is just in case someone comes across this thread using the search function.
The Vietnamese Government have made it easier in the last couple of years for 'foreigners' to buy land/property.
That said, depending on the exact location, it can still be fraught with danger.
The local interpretation of 'freehold' is that you own the land or the land a property is built on for 50 years (so in reality it is actually 'leasehold') with the "possibility" to extend that for another 50 years.
It is still a much simpler process for a Vietnamese to buy a property or land (and cheaper too) but you have to remember at all times that at the end of the day, the Government owns the land and regardless of what legal contract is drawn up, they can still buy that land back.
They do compensate you for land they buy but their market value will be much less than your own value given they won't usually offer compensation for any building on that land.
We bought a house on a private estate (Q9) last year and the security of tenure is "Indefinite", meaning not limited to 50 + 50 years. It is just about certain (well, as certain as anything is certain here) that the tenure will not be less than 50 / 50, because the land here is earmarked for private dwellings and other areas locally are earmarked for commercial development.
There will be a lot of crying in Q2 fairly soon when the government start to implement their plans for moving government buildings to Q2 from Q1, although a lot of the ground clearance has already been done.