Ten days is enough for a Thailand island trip if you resist the urge to see every ferry port on the map.
Start with Koh Samui for easy arrivals and a soft landing. Move to Koh Phangan for quieter beaches outside the party calendar, then finish on Koh Tao for snorkeling, diving, and slow scooter days.
The mistake is packing the route too tightly. Ferries take time, weather changes plans, and the best parts of island travel often happen when you stay put long enough to learn the rhythm of one beach.
Book the first two nights, keep the middle flexible, and protect your final night near the airport or ferry connection. That last buffer saves more stress than it costs.