@Ian *********
it takes about an hour to get to the border and another hour to get to Vientiane after entering Laos, so it's still much quicker to just go to immigration in Udon Thani. And, that border often says people can't come back immediately, or doesn't allow exit if they suspect someone will do a a visa run. Two friends were recently not allowed to exit there (separate occasions) and were sent to Bangkok to fly out.