Saisettha, 11km east of Attapeu on Rte 18B, is a sizeable village on the north bank of the Se Kaman (Kaman River). It used to be a small, quiet village with a good vibe, but it's mostly outgrown that; however, art lovers will appreciate some of the temples here.
Just past the Houay Phateun Bridge, turn right to the peaceful riverfront Wat Siliawat That Inping (aka Wat Fang Daeng), which has a large octagonal stupa. Inside the adjacent hall is a rather complete set of paintings telling the Wetsandon Jataka (the Buddha's penultimate birth) tale.
Just over a kilometre to the east, at the end of the road, the sala (open-sided shelter) of Wat Ban Xai has more adroit mural paintings, focusing mostly on the Buddha's life story. The old ubosot (ordination hall) has some original floral stucco work on the front.
From Wat Ban Xai, go back to the highway and continue east. Take a sharp right at the first large road after crossing the Se Kaman bridge and continue to the second temple you meet (6.5km total) in Muang Kao (Old City). This is Wat Luang, famous because the Lan Xang King Setthathirat, for whom the district is named, is buried here. The temple was supposedly founded in 1571, the year of his death, and the stupa in which he is interred was erected soon after, though it has been rebuilt since then. There's also a crumbling old wihăhn (temple hall) with a large Buddha inside and some original woodcarving on the front gable and door. The little ubosot in front is in better shape.