Looks good, very keen to try it. The vietnamese fruit you are referring to is Longan (they are similar to Lychees) and you should be able to get them at any asian grocery store.
This is a very flavorful drink. It's kind of like a dessert because of the sweet coconut milk. It takes some time to make, but the outcome is completely worth it. The layers of flavors work so well together. The presence of the other ingredients make the drink not too sweet. Definitely one of my favorites.