Dont go cam, you might be able to get stamp back at cam side, as they have a law that says you need to stay for 24 hours. Go buy a bus ticket at nakornchai air to nong khai, and take a tuk tuk (80b) to the thai custom, than get on a 30b bus to lao custom. Very comfortable bus with toilet and they will give you drinks and food.
can not, you have to fly in, get all the documents and go marry at the khet, than go apply for the marriage visa. (not easy, you will need a document to say you are single from your own country, police check, copies of everything translated and stamp by mfa, than go to your khet.) it is a nightmare, lots of paper work.
