Normally the boats race used be on Namkhan river in Luang Prabang.
The boat race on these pictures is look like on the Mekong river. The back ground of pic 3 showed a building ( house ) on top of a hill look like a Monk temple on other side of the Mekong river and is about 3 Km north of Ban Xiangmain. I might be wrong cause more than 40 years that I was left my birth place, Ban Wath Nong, since I was 14.