I don't know how some people can sleep with such an exciting trip ahead!
The train left Bangkok at 6:30pm and arrived in Trang (southern Thailand) late the next morning. We were in the sleeper car with one bunk on bottom and another flipped down from the ceiling. Comfortable and economical at 500 thb ($15).
Next we had to take a minibus to the Hat Yai pier, then 3 hours by ferry to reach Koh Lipe. The island is only about 35 miles from Malaysia.
The island has a little walking street with clothing shops, souvenirs, restaurants, and some low-key bars. The general vibe was quiet and relaxed. The whole island itself is very small, and you can easily walk anywhere you want to go.