While most of the ASEAN nations have been dictatorships and or communist regimes for some time, they are starting to realize that they need to move into the world of the capitalist markets and are thus in the process of opening their stock markets and currency markets to the world.
Thus Cambodia for example just opened their very first stock exchange, which, as of this writing is trading a single stock (the Phnom Penh Water Authority). The Ho Chi Minh Stock Exchange was opened a few years earlier in the year 2000 and already sports more than 300 companies traded on the exchange. In Laos, the Laos Security Exchange is also a recent creation with just two stocks being traded on their market.
All Trying to Attract Foreign Investment
The key thing to remember however is that all of these countries along with the other ASEAN nations (and especially Singapore, which has always attracted foreign investment) are eager to attract foreign investment and are thus ripe investment opportunities for those who wish to take their chances in exchange for potentially large rewards.
How to Invest
One of the best ways to make investments in these countries is to look into working within their stock markets. Since almost all ASEAN nations now have a stock exchange (the exceptions are Brunei and Myanmar, though a Burma stock exchange is currently being planned and there are murmurs about creating a stock exchange in Brunei as well) it's possible to simply purchase stocks in the various countries as an investment.
Be sure to track the various companies just as you would with more traditional investments in more established countries. It may also be a good idea to hold off on investments on the newest stock exchanges until they have matured somewhat, unless you can afford to lose the money on your bets.
Forex Markets
Most of these countries have limited Forex markets available for investing opportunities, though it is possible to purchase currencies in some of these countries as well. The Lao Kip is a good currency for going short since the currency has been steadily dropping in value versus the US dollar over the past few years. The Vietnamese Dong by comparison has been steadily rising in value when compared with the dollar. The Cambodian Riel has seen the most fluctuation of all of these currencies, with the price jumping up down against the dollar. In all cases remember that as currencies of emerging markets these are likely to be much more volatile than purchasing currencies from more established states.
Bottom Line
The bottom line is that there are investment opportunities which are a off the beaten path that are worth looking into, especially if you have the stomach for slightly riskier investment opportunities and a good handle on the Forex world in general.