I spent some time on Koh lipe and was fortunate enough to find the Karma Bar on the beach in front of Mountain Resort. The beach on Pattaya was abit crowded and noisy at night with all the competition from the other bars. Karma was all by itself and the staff was top notch. It was the only bar that made proper cocktails and even shakes for my kids. They even do fireshows at night on the lovely spit in front of the bar. If you go to Koh LIpe, go to Karma and give them a hug.
In the middle of the island, is Pooh's Bar. This is where everyone invariably ends up at nights or even during the day... it's a great place, run by Pooh and his cousin Noi... (say hi to them please and tell them Winnie recommended you!)
There's also Jack's Jungle Bar by Sunset Beach, and Moonlight Bar on Pattaya Beach.
Dress Code: Laid back, casual, less is more