I have a good bicycle which I would like to donate to my Lao friend. How can I get it to Nong Khai and pick it up by myself afterwards (a couple of days later).

 

Also is it possible to ride with bicycle from Nong Khai to Vientiane?

Send it by the Post Office, they'll even wrap it for you

Don't see any reason why you can't nice from Nong Kai to Vientiane 

Ride from Chiang Mai to Nong Khai. Then Nong Khai to Vientiene.

Take the bus CM to NK, put the bike in the bus luggage area, or on the roof if a 3rd class bus. I have no idea if there will be any difficulty taking the bike across the border, but there may well be, it is a vehicle after all. Perhaps you should do a Google search for a cycling club in SEA and ask there.

15 minutes ago, grain said:

Take the bus CM to NK, put the bike in the bus luggage area, or on the roof if a 3rd class bus. I have no idea if there will be any difficulty taking the bike across the border, but there may well be, it is a vehicle after all. Perhaps you should do a Google search for a cycling club in SEA and ask there.

My cycle club in Loei went across 2/3 years ago

Visa on arrival is reliably available at most overland crossings between Thailand and Laos, including the Huay Xai, Vientiane, Savannakhet, Tha Khaek and Chong Mek entry points. It is also available at both Vientiane and Luang Prabang airports (US$37, cash only, one passport photo).

I have ridden my bike both ways VTE to Udon and back.  Ship your bike from Bang Sue to Udon or Nong Khai.  Do yourself a favor and print the Lao immigration visa form, fill it out, paste a photo on it and have 40 USD , or same in THB or Euro.  I have ridden the bike through the motorbike lanes both sides.  Might need to park the bike with motorbikes and clear as they do.   Never had an issue.

People cross the Thai/Lao border all the time with bicycles.  It's no problem at all.  Lots of people cycle from Vietnam to Laos and then on to Thailand at various border points including the one you intend to use.

I've cycled the friendship bridge from Laos to NongKai.  It's permitted but not exactly cycle-friendly.  The lanes are narrow, with little room for large coaches to pass by.  There is (or was then) a walkway on the edge, separated from the road by meter-high concrete barriers, but you can't ride the entire length due to large signs bolted down blocking the way.

 

 

 

Much better crossing for bicycles is Kennetau (Laos Hwy 4) near Loei if that's convenient for you.

 

13 hours ago, NORDO said:

I have ridden my bike both ways VTE to Udon and back.  Ship your bike from Bang Sue to Udon or Nong Khai.  Do yourself a favor and print the Lao immigration visa form, fill it out, paste a photo on it and have 40 USD , or same in THB or Euro.  I have ridden the bike through the motorbike lanes both sides.  Might need to park the bike with motorbikes and clear as they do.   Never had an issue.

How long was your one way trip between the cities?   I am assuming you mean bicycle when you write bike.