whats the fastest way from vientianne to udon thani? where can i find bus schedule and how long is the ride? where can i buy tickets? thanks

There are buses that run from the Talaat Sao (Morning Market) in Vientiane direct to Udon Thani.
More Info/Timetable/Fares
as above, although I always heard it referred to as the central bus station, as soon as you get into Vientianne book the ticket, if full then get bus to Non kai bus station and there are regular buses to Udonthani. If that is booked up then get the local bus to border [last row and goes direct to immigration,] then other side shared tuk tuk to Non Kai bus station; then buses everywhere you could want to go, also from there, is a direct overnight bus to the new airport BKK.
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<hr>get a bus to the border then a train from Nong kai to udon <hr></blockquote>
Why? You will waste your time sitting around waiting for train. This is not a commuter type of train with less frequency. Hop on a bus or hire a Tuk Tuk and you will be in Udon in 40 minutes.

I just had a look at the TAT link above and I think that is slightly out of date. From memory (and I'll try and double check from the VTE end tonight) there are another 2-3 buses daily to Udon.
Dom.

click here
someone posted the above link some time ago, somewhere near the bottom is a photo of the 'Vientiane-Oudonthany' bus timetable posted at Talat Sao bus station. took about 2 hours this August (not much of a queue at Friendship Bridge immigration). ticket office at bus station.
wonder if there will be less passengers on this bus route after Tiger Airways stops flying to Udon Thani from November onwards.

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<hr>wonder if there will be less passengers on this bus route after Tiger Airways stops flying to Udon Thani from November onwards.<hr></blockquote>
Which is about when AirAsia will start direct flights from Kuala Lumpur to Vientiane, too ...
I took a tuk tuk from Vientiane to Xieng Khuan Buddha park and Friendship Bridge and crossed the border. Upon arrival at the border gate at Nong Khai, you will see an Information Center and some Thai staff will provide you info about the bus to Udonthani.

The link is out of date as I took the 1400 bus from Vientiane to Udorn last June and it is not listed on that link
Note they were NOT selling tickets for the bus until the previous one had left. This meant I could not buy a ticket till1145 (they had a 1130 bus) for the next bus the one that was leaving at 1400. No problem getting a ticket but I had been there at 830 AM and had to go back at 1130 to buy the ticketl

#8: are you referring to the TATnews link in #1? photo of the timetable in the link in #5 shows departure times at 08:00, 10:30, 11:30, 14:00, 16:00 & 18:00 for the Vientiane to Udon Thani route.