Luang Prabang is a holy place, so don't expect to find cheong places. There are many backpackers there you might be able to hook an angmoh up if you're skilled or lucky. I suggest Vang Vien if you wanna see some skin and flesh. Super backpacker and budget and you can see angmohs going around in bikinis. Easier to hook up there cos people are half drunk most of the time. Or if you feel rich you might try to offer cash to the angmohs and see if they are tempted. They travel long periods and the extra cash would be useful to them to drink more. Many angmohs like to stay in Vang Vien for weeks. Lol.
For cheong places like clubs and ktvs, Vientiane is the place to go. I've never been to ktvs there but clubs mostly close early except for Don Chan Palace. They have a club in the upper levels and many people go there. Beware of LBs though
Have fun and good luck!