Roundtrip to Nam Ngum Lake
The usual spots for tourists to see in Laos are Vientiane for one night, then Luang Prabang and maybe Pakse. But there are many more places to visit. For example, Nam Ngum lake.
Leave Vientiane on Highway 13 east and follow then Highway 10. On the way, you can make some nice stops.
First is the Lao Zoo. It might be not as big as the ones in your home country, but it is actually worth a visit. They have crocodiles and deers, gibbons, bears, many different species of birds.