Koh Sichang

Tiny Sichang, a short boat hop from the town of Si Racha, an hour east of the Thai capital, is the nearest island to Bangkok yet has never made it onto the travellers' circuit. There's decent accommodation, thick jungles, an abandoned palace, excellent aharn talay (seafood), monkeys and a small sandy beach.
See ko-sichang.com for accommodation.

Koh Tarutao

Set in the furthest-flung southern corner of Thailand's Andaman coast, 26km long Tarutao has incredible forest-rimmed beaches, wild jungles and no mod-cons. It is part of the stunning Tarutao national marine park, which comprises 51 islands including gorgeous Koh Lipe. Accommodation and food here are basic, but it's all the better for that.
See kohtarutaoisland.com. Tents for rent from £2 a night, bungalows from around £8. Open November-mid-May.

Koh Phayam

Up near the Burmese border, a two-hour boat ride from the town of Ranong, Phayam has slowly emerged as the sleepy island of choice for travellers eager to avoid the over-development of Phangan and Samui. Huge, arcing sandy beaches, excellent snorkelling, no cars and plenty of cashew trees and hornbills set the scene.
Bamboo Bungalows do what they say on the tin. There's also a tropical garden, Wi-Fi, motorbikes, surfing, snorkelling, fishing and volleyball.

Koh Jum

A short hop from the famed travellers' hub of Krabi, Jum certainly lacks the glamour of its near neighbour, Phi Phi. But this is an island to lose yourself in for weeks at a time, cut off from the world and working on your tan. Don't expect the best beaches but you will find a smattering of decent bungalows, villages of chao ley (sea gypsy) people, dense jungle and a soporific travellers' vibe.
See kohjumonline.com for a handful of backpacker places or the more upmarket bungalows of Koh Jum Lodge.

Koh Phra Thong

Koh Phra Thong 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 "road" that's a sandy track. The Golden Buddha Beach Resort is the only resort on the island, with 21 traditional Thai-style wooden houses set in the coastal woods. Swim, get a massage, canoe the tidal river, snorkel in the lagoon . . . and that's it.
Doubles from £49, room-only.

Andrew Spooner is the author of Footprint's Thailand Islands and Beaches guide (£13.99).