Thailand's last unspoiled islands

Koh Sichang

Koh Sichang is situated 100 km from Bangkok and less than an hour from Pattaya. The island boasts beautiful beaches, great snorkeling and biking in spectacular scenery, temples and palace ruins. Fish, rent a kayak, meditate or learn massage. 
ko-sichang.com

Koh Tarutao

Set in the furthest-flung southern corner of Thailand's Andaman coast, 26km long Koh Tarutao has crisp white sandy beaches, wild jungles, friendly atmosphere, azure clear water and easy going style. This is what makes Tarutao Island the perfect Thailand holiday getaway. The island is part of the stunning Tarutao national marine park, which comprises 51 islands including gorgeous Koh Lipe. 
kohtarutaoisland.com

Koh Jum / Koh Phu is a small island situated between Koh Lanta and Krabi town. Whilst the southern end of the island is known as Koh Jum (‘Jum Island’), the northern part bears the entirely different name Koh Phu (‘Phu Island’). The island’s beaches and jungle-clad mountain are still almost perfectly pristine. The low visitor density, plus the ease of access from Krabi airport, currently make Koh Jum southern Thailand’s most accessible hideaway island.
kohjumonline.com

Koh Phra Thong - Golden Buddha Island - is another unspoilt island in the Andaman Sea off Thailand's west coast, near the town of Kuraburi, with around 16km of empty, golden beaches, no cars and one sandy track serving as "road". The island is named after a local legend. The story tells of a precious stolen golden buddha statue buried on the island by pirates which was never recovered. Koh Phra Thong is an ideal choice for those who are really looking to get away from it all.
kohphrathong.com