Cannot help you with any start ups going on, or the business side of things, but can give you some advice in general.
Be very careful when it comes to your Vietnamese partner, which you have to have for a business, unless your thinking big time venture. I've seen a few expats get turned over by their VN partner, best of buddies at the start, expat puts all the effort in, becomes a success, VN partner doesnt like to share profit, bye bye expat !!
Iam sure this happens in most Countries that you have to have a local partner, just here they seem to smile at you when your getting stiffed.
Hope there are new rules to help avoid this, iam sure AmCham will let you know if there are.