How much time does it take to pick up a visa in Vientiane to catch a 6 pm flight from Udon Thani?

Why so little time ? Is this Los Angeles, New York, London, Sydney ? Take a deep Breath - this is Thailand ... why drive yourself to a heart attack

Just did it. 1.30 pick up, out in 30 mins. And a huge queue. Get a taxi to the bridge. Then a bus - they come often. Then there are plenty of vans around. There's a Nok Air van stop, although not free for all Nok flyers. I left my hotel at 8 for a 1.30 flight to be on the safe side, but got to airport at about 11.15. So yes, six should be fine if you pick up at 1.30. How early you get there doesn't matter however, as you must wait for your number. Mine was 120, and it took about 30 mins from the time I got there. If you are 300, that could be different. You can also get a taxi and miss the vans, but that will cost you.

Took me about 20 mins to pick mine up. But I had a very very low queue number.

yes at a push if you get to the embassy and are near the front of the queue. and arrange transport right through to Udon