Vietnam has been accepted as the 150th member of the WTO. As part of the process of integration, it will be forced to reduce tariffs on imports from about 18% to about 14%, which will cause a hit on its budget, but will in turn be able to ignore other countries' import tariffs on many goods. Vietnam will also have to rescind its policy of limiting foreign ownership of businesses in Vietnam.
Vietnam is only very, very nominally "communist" at this point. Much like China, it "is what it is" -- totalitarian, with the people in charge planning on staying in charge, but with a thriving capitalist economy. This demonstrates, once again, that capitalism and democracy don't always go hand in hand.