Which Thai islands work better for families?
For many families, Koh Samui, Phuket and Koh Lanta are the easiest places to start. Samui suits an easy resort stay, Phuket suits families who want a very wide choice of hotels and activities, and Koh Lanta fits a slower beach trip if a little more transfer friction is acceptable.
Full answer
For many families, Koh Samui, Phuket and Koh Lanta are the easiest places to start, but they suit different trips. Koh Samui works well when you want an easy resort base with plenty of food, services and simple beach days. Phuket is the more built-up choice, with a very wide range of hotels and activities; that convenience comes with a busier, more urban feel. Koh Lanta is quieter and slower, which can be a better fit when the family mainly wants beach time and is comfortable with a little more transfer friction.
Smaller or more boat-dependent islands can be wonderful, but beautiful and easy with children are not the same thing. Rough crossings, limited transport and moving luggage between boats matter more with tired children than they do in an island-hopping fantasy.
Pick the island for the season and the family, not for a universal ranking. Check current ferry and flight schedules, weather conditions and hotel transfers before locking the route.