The commitment to heritage preservation in the old city centre of Luang Prabang means that no hotel in this part of town has a swimming pool. Many of the hotels outside of the centre have swimming pools, however, and there are several community pools, including an Olympic-size municipal pool at the athletic grounds near the new bridge on the way to the airport. Most pools will require an entrance fee.
In the hottest months, March to May in particular, temperatures can be very high, and a cool off in a pool is a welcome relief. Ask around. A short tuk tuk ride will get you to most of the popular swimming pools.