Is it still easy to obtain a Thai visa in Vientiane, Laos, and what transportation options are available from Chiang Mai?

@Nikola ***********

Yes that's the one to avoid (Aranyaprathet-Poipet). All the buses go through there. None of the other border crossings have cross-border bus services but that's just the nature of things.

The smaller crossings between Thailand and Cambodia are OK but as you have already chosen to go to Laos, the fact that Thailand and Laos operate more than 10 cross-border bus routes, which makes travel a lot easier for those without a car and Thai-Lao immigration checkpoints are a lot more easygoing in general, all point towards using Laos as the place you want to head to.

@Nikola ***********

It's not too bad at all. It's just the Bokeo-Boten section, which can be covered in as little as 3.5-4 hours by minivan or private transfer, that needs to be done by road but once you're in Boten, the train is super fast and whisks you down to Luang Prabang in no time. It takes about 2 hours. Then it's 1 hour from there to Vang Vieng or as little as 1h50m to Vientiane from Luang Prabang, if you're on the express service.

If you fly from Chiang Mai to Luang Prabang, you might be obligated to purchase an outbound ticket from Laos as one way tickets are usually frowned upon by airlines. Lao Airlines flies this route and I was reading Bangkok Airways does too (but check again, as Bangkok Airways is notorious for starting services then quietly ending them just months later). The airline might still let you fly on a one way ticket, but generally, it's a lot less flexible than if you go by land.

You could also do the slow boat from Huay Xai (Bokeo, Thai border) to Luang Prabang and thus avoid the roads.

Almost everyone uses the train instead of the roads on the north-south journey, unless they come by car or like adventure. If you enjoy adventure, then you'll have no problem with the highway trip from the Thai to the Chinese border, where you catch the train. The road trip from Luang Prabang to Vang Vieng is much more nausea inducing and often takes longer as well.

@Nikola ***********

the requirements changed within the last year and they became very strict. Every consulate in Southeast Asia.