Where do I go for my visa interview in Vientiane, Laos?

Go to the post office. Best place for.

Same place you paid, but the building to the left. I queued at desk 5 and was given a number. Everything was running about an hour late. The interview guy wasn't overly friendly but he was nice and there was no pressure. He asked what I was doing (cooking classes) and to tell him about it (I'll be looking at traditional ingredients and techniques etc) and how many months I booked for, also the name of the place. He asked to see the bank balance, and also how I'll support myself; I said I work online, and he asked for the name of the company and we confirmed no Thai clients. He asked to see one payment from them within my bank statement (all done on mobile phone - get a SIM card!) - extra info: I get paid into payoneer and withdraw to my bank so my company name wasn't there but he was satisfied just for me to point out a payment.

That was it. He said I would probably get the result the same day, which I did, but I don't know if I had a quiet week, it might be different / busier for you.

Don't worry, it was all chill. I took my documents with me from my school, but he didn't ask to see them

Go to the same compound, the lobby of the building just to the left of the payment window.

Someone just posted today the list of docs for their interview they had in Vientiane. It will not be to the payment window. You were asked to come the embassy?