What actually wears a child out
Parents usually worry about the sea and the food. In practice three other things cause the trouble: sun, long drives and the fixed timing of group tours.
Phuket sun burns in 20–30 minutes even under cloud. Children's skin burns faster than adults', and one such day can ruin the rest of the holiday. Only three things work: a sleeved swim shirt, sunscreen every two hours, and shade between 11:00 and 15:00.
Driving. An hour on mountain roads is nothing to an adult; to a three-to-five-year-old it is already a trial, and with motion sickness it is a guaranteed problem. When assessing a route, add up the travel both ways: sea trips spend 4–6 hours purely on movement.
Group format means someone else's schedule: if your child falls asleep, tires, or wants to eat off-timetable, nothing can be adjusted. That is why for families with toddlers the private format often pays for itself in nerves rather than money.
Under 3
Full tours are best avoided at this age. The realistic maximum: the beach, a short island drive with air conditioning and a return in time for the nap, and a water park with a toddler pool.
Speedboat sea routes do not suit: the hull slams on the swell, life vests fit toddlers poorly, and there is almost nowhere to hide from the sun on board. If you really want time on the water, take a private boat with a canopy and a soft ride.
Ages 3–6
Here the real choice opens up. What works well: an ethical elephant sanctuary (feeding and mud baths are the big hit at this age), the Andamanda and Splash Jungle water parks, Coral Island with its gentle entry and 15-minute crossing, and island sightseeing with air conditioning.
Moderately suitable: James Bond Island — a sheltered-bay route with almost no motion, though the day is long; and Khao Lak with bamboo rafting on a calm river.
Not recommended: the Similans and the 11 Islands — three hours each way on open sea; the one-day Cheow Lan trip with its 5 am start and 13 hours of travel; and riding a quad bike.
Ages 7–12
The age when nearly everything is open. Phi Phi and Krabi with snorkelling work beautifully — children this age usually swim confidently and spend more time in a mask than the adults. Ziplining is allowed from 4 but teenagers enjoy it most. Rafting, quad biking as a passenger, Tiger Kingdom, shows.
Diving is available from 10 as a discover dive with an instructor: limited depth and the instructor within arm's reach throughout.
Still demanding: the Similans and air tours — not for interest but for sheer duration.
Practicalities: prices, car seats, packing
Every route has a child price, usually 200–400 THB below the adult rate; water parks price by height rather than age. Under-3s are usually free but do not get a reserved seat on the boat.
Child car seats are not standard equipment in Thailand. We fit them on request — tell us at booking, not on the morning of departure.
Packing: SPF 50+, a sleeved swim shirt, a hat, a change of clothes, water, a familiar snack (the route food is Thai and may not suit), water shoes for rocky entries, wet wipes, and children's antihistamine and motion-sickness medicine agreed with your own paediatrician.
How to shape the day
The pattern that works with children: an early start, the active part done by 11:00, lunch and shade through the hottest stretch, back by 16:00–17:00. Anything ending after 19:00 will be paid for the next day.
Do not book two tours back to back. A day by the pool in between is not lost time — it is the condition under which the second tour goes well.
And be honest about evening shows: Fantasea and Carnival Magic end around 21:30, with another hour back to the hotel. For a child under 6 that is too much — Simon Cabaret is shorter and finishes earlier.