The good thing about Koh Samui and Koh Pha Ngan is that they're both a fair size. This means there are plenty of white sandy beaches and tropical highlands to go round. You don't have to book into an all-inclusive, or pack your ear plugs to cope with noisy neighbours every full moon. Accommodation ranges from boutique spas and exclusive beach front properties, to family friendly resorts and honeymoon hang outs. Seek out areas away from tourist hot spots and you'll find local markets, jungle trails and excellent bays for snorkelling. Koh Tao and Khanom are far less frequented and promise an even more natural experience.
Obviously there's a lot more, this is just to get you started...
Although sections of Koh Samui are very crowded (we're looking at you, Chaweng) there are just as many that have retained the sleepy fishing village rhythm that initially drew travellers here decades ago. The north coast, especially, has a particularly relaxed and more traditional Thai vibe. This is where islanders come for fresh ingredients at Hua Thanon's wet market, or to tuck into the catch of the day off the wooden pier at Thong Krut. Beach front properties overlooking Bophut Bay are really beautiful, and tend to work in harmony with nature and local communities rather than against. It's a large island and has just as many exclusive adult-only enclaves as fully-facilitated beach resorts, with shallow bays for snorkelling with the kids.
Koh Tao has the right balance of boundless natural beauty and just enough activities to tempt you from the beach. You can borrow a bike and follow jungle trails, canoe around the coast, or hire a long-tail boat and seek out secluded spots for snorkelling. The underwater scenery is straight out of National Geographic. It's no wonder Koh Tao is one of Thailand's premier dive sites. The beach resort at Haad Tien is one of just a handful of places to stay. You can pad over reclaimed wooden boardwalks or stretch out in a hammock surrounded by tropical flowers. And there's no better way to balance your day than watching the sun set over Thian-Org Bay with a couple of Mai Tais at the bamboo beach bar.
Koh Pha Ngan's local community have had a chance to reset and shift their outlook on tourism. Backpackers still flock to Haad Rin's hostels, but there are also some upmarket beach boutiques that are well off the raver radar. Properties are sophisticated, yet still sandy, and provide a much more relaxed setting to while away moonlit evenings.
If you'd prefer to steer clear of the island ferry altogether, Khanom on the mainland peninsular is really underrated. This lesser-known section of the south east coast is made up of fishing communities and has, so far, avoided any major development. Check into one of Khanom's exclusive spa resorts for the chance to sink into white sands and see Koh Samui from a much more peaceful perspective.