The pagoda and chapel of Wat Phon Chai
Wat Phon Chai is the center of activity for the Phi Ta Khon festival in Dan Sai. It's hard to say how old the temple is, but it was probably founded several hundred years ago at least. The main buildings are just a small chapel and a square pagoda (prathat) next to it. During the festival, there are usually several activities going on around the temple grounds, as well as it being the final destination for those taking part in the processions.
Dan Sai Folk Museum
The Dan Sai Folk (Phi Ta Khon) Museum, in the grounds of the temple.
The Dan Sai Folk Museum is located in a finely detailed teak building in the grounds of the temple. The museum is devoted almost exclusively to the Phi Ta Khon festival, and will give you some good background information on the event.