The tiny island of Koh Tao ("Turtle Island"), 45 km north of Koh Phangan, is one of the top scuba diving destinations in Thailand, if not the world.
Koh Tao is now also a destination for wild 20-somethings to warm up before or unwind after neighboring Koh Phangan’s Full Moon Party. Fortunately, despite its quite small size, most of the beaches around Koh Tao have retained a charming, laid back atmosphere and bungalows ranging from ultra-basic thatch roof to chic and boutique are available for those on any budget to enjoy the beauty of one of Thailand’s most spectacular islands.
(http://www.tourismthailand.org/where-to-go/cities-guide/destination/ko-tao/)