How to Experience the Best of Trang, Thailand’s Treasure Islands The 40-square-kilometer Koh Libong is Trang's biggest island. It's home to one of Thailand's last wild dugong populations. Longtail boats can be hired for dugong watching tours and cost about $35 for three hours. Closest to the mainland, Koh Mook has several modest resorts to choose from, including the Sivalai Beach Resort (pictured), which occupies a stunning beach promontory on the east coast. Most visitors head straight for one thing on Koh Mook -- Morakot Cave. At low tide, visitors can swim through the pitch black cave entrance to access the hidden beach on the other side. According to legend, the hidden beach was once a secret hideaway for pirates, who came here to stash their ill-gotten gains and escape the long arm of the law. The most popular island of the bunch, Koh Kradan is famous for its stark white sand and clear waters. There's a reef located just off the beach. If you're not a strong swimmer, you can walk out to it at low tide. From Koh Kradan, three smaller islands can be seen offshore: Koh Ma, Koh Chueak, and Koh Wan. Locals can sometimes be seen climbing through thick ropes to look for the edible nests of the swiftlet birds, which make their homes on these three small karst outcrops. Koh Ngai is actually part of neighboring Krabi province but is only a short ride from the Trang mainland. Out of all the islands in the archipelago, Ngai has the most unspoilt jungle, which is home to roving monitor lizards, monkeys and a huge variety of birds.