Upvote:2
It seems to be an intermittent stream about 30km from Savannakhet, not Vientiane. As for spelling, you can take your pick from Houay Dènmuang, Houei Den Muong, or Houei Dên Muong. Or ຫ້ວຍແດນເມຶອງ if I have it right.
Upvote:3
Found it. It has a Facebook page but it's a bit unclear as to whether it's a restaurant, a guesthouse, or something else.
The Facebook page has the English subtitle "country house" and a few of the photos are of plates of food but others are of people. Zooming into the map that Facebook provides makes it look like it's within the grounds of Pakpasak Technical College, but often these map pins are just in a random spot of the city. Switching to Google Maps for directions from there, Google associates that spot with the name "Hope Academy". It's in the main central area of Vientiane but I can't really associate it with any main POIs.
Whatever it is, I wouldn't be surprised if it is named after the town near Savannakhet mentioned by TonyK.