Huay Xai recommended

This town isn’t much more than a haven between Laos and Thailand. Not much to do, not much to see.
You might spend a night before catching a slowboat to Luang Prabang. Or:

– Do:
It’s hometown to The Gibbon Experience, a zipline paradise in the beautiful Nam Kha national park. Take the time (3 days, 2 nights) and set aside the money (220 euros) to fall in love with this jungle and it’s countless inhabitants – even if some will scare you.
Make sure you get treehouse number 7, or otherwise 4.
Bring some snacks and sodas from the last village

– Eat:
If you walk a little out of the crowded area, following the main road left from the pier, you’ll find some local shacks.

– Drink:
Rigth before sunset the balcony up on Friendship Guesthouse is a nice spot to hang out.
In the main street you’ll find some entertaining bars.

– Sleep:
(don’t)Friendship Guesthouse: I caught bedbugs in two different rooms and we had some strange treatment. That’s what you get for picking the cheapest.

I however have heard good things of Sabaydee Guesthouse.

BAP did have a curfew, but I also heard it’s run by a very friendly lady.