@Camille ******
that's what I found on REDDIT about a border run in Chiang Khong to Huayxai : "For anyone doing the border run from northern Thailand (closest land crossing to Chiang Mai and Chiang Rai) you can no longer turn around and immediately get back on the bus back to Thailand after getting your Laos stamp/visa. They are now requiring a two day stay in Laos before returning. When you do come back you need to have proof of 10,000 bhat, T30 and proof of exit (flight info).
I did this run 3 months ago and it was not in effect back then. Not sure if this is just this crossing or all land crossings. I read some comments that say it’s shady and the head of the immigration here must be getting some kind of cut from the Laos side. No idea the truth of that but I do know there are signs everywhere and all the agents and peripheral businesses act like this is the new normal.
The guy that runs the daily van from Chiang Mai says he can still get you in and out the same day because he’s so connected in there and that’s his whole business but again, can’t say for sure. All I know is I’m spending an unexpected two days in Laos, which is fine, just wish I planned for it better so that’s why I’m telling you."