The Junk Liveaboard
The Junk is a very cool boat with a very interesting history including being used in a James Bond film. The cabins are adequate and there are plenty of places on the boat to hang out. The boat is well maintained and didn't have any issues with leaking cabins or broken toilets on my 10 day trip. Food is plentiful and good with a mix of excellent Thai food and some western cuisine. The crew were excellent and a lot of fun, and they brought us to a few beaches to hang out.
One of the coolest things about The Junk is that you get to help raise the sails in the old school way on the last day and go sailing.
Schedules and itineraries vary and they do go to some of the best dive sites in Thailand like Hin Daeng and Hin Muang and Richelieu Rock.