Of course, there’s nothing wrong with working out in a gym in Vang Vieng. Still, it shouldn’t be necessary. In Vang Vieng you have many options for doing sports. For example, you can climb the Pha Ngern View Point, swim in the lagoons, canoe, or hike in the jungle. All of these activities should make you tired. Afterwards you probably don’t even want to go to the gym anymore.