So a few days ago I decided to just hitchhike from "downtown" Vientiane to the Buddha Park and see if I would just stumble across some guest houses on the way. I departed quite late and didn't get any rides before it got dark so I only got as far as I could walk before too many angry dogs made me not want to push on.
I only got about one quarter to one third of the way and did pass a few guest houses. The one I stayed at was indicated on Google Maps with a slightly different name than on their road sign. Somvang Guesthouse or Souksomvang Guest House.
It's almost opposite the site of the new US embassy under construction but it's still 16.5 km / 10.5 miles from the Buddha Park. So further away than the resort that uncovery found and not within strolling distance. It is on the main road to the park however and it is cheap.
Google Maps indicates guest house but not US embassy. OpenStreetMap indicates US embassy but not guest house.
The problem is that it's disgusting. It looks quite fancy from the outside but these days it seems to be mostly used by prostitutes working in some of the "bars" or "night clubs" along the highway. For 60,000 kip ($7.60 / €5.70) you'll get a room with a fan and bathroom. The floor, toilet, sheets, and towels will be clean but nothing else. There were cigarette butts and condom packets nobody bothered to get rid of. But there were no bed bugs.
If you somehow end up here and can't get to the city itself and have low expectations you could crash here if you really had to.
The next morning I got rides easily. I thought I saw one or two guest houses a bit further but can't be sure as I was in a moving car on an extremely bumpy road.
On leaving the Buddha Park I headed further down the road away from Vientiane to see if there might be a guest house nearby in the other direction since there is more or less a village there. A local who knew some English told me there were no guest houses so I turned back.