You can invest in Vietnam
I've lived in VN for over 10 years and work for a property developer and real estate management company.
The law only allows resident foreigners to invest in certain types of property for their own use for 50 years. Eligible foreigners may not legally lease out their property (i.e. use as an investment) and if leaving or losing the right to stay in Vietnam, foreigners have 12 months to either sell their property or give it back to the state.
That said, there are limited opportunities for foreigners living outside of VN to legally invest via a holding company (say in HK). This has been successfully done for a couple of beach front projects and the prices are quite OK. Tax breaks are available usually for the first few years in the onshore company and dividends are currently taxed at only 5%. In HK, tax is user friendly.
I have a Dutch friend who has a small resort project of only 100 units on 3 hectares (long frontage - most have ocean views) of prime beachfront land which he's selling from $120,000 (all in for a 1 bed, furnished apartment). It is approx 80% sold-out and is due for completion by early 2012. Some foreigners have invested and I believe it's a pretty safe bet if you are comfortable to put money outside of your home country. They anticipate 20%+ IRR but this might be a little ambitious with the number of resorts coming on line. 20 free nights per year come with the deal.
I hope this helps
Cheers,
Mal