Route 1: culture first, beach last
Bangkok 2 nights → Ayutthaya day trip → Chiang Mai 3 nights → Phuket 3 nights. This is the route in our Thailand Highlights tour and it works because the beach comes last, when you actually want to stop moving.
The only real cost is two flights: Bangkok–Chiang Mai and Chiang Mai–Phuket, both around an hour and cheap if booked early.
Route 2: the north only
Bangkok 2 → Sukhothai 1 → Chiang Mai 4 → Chiang Rai 2. No beach, no flights except home. This is the best route for food, temples and mountains, and it is noticeably cheaper.
Ten days in the north lets you do an elephant sanctuary, a cooking class and Doi Inthanon without ever feeling rushed.
Route 3: the Andaman
Phuket 3 → Phang Nga 1 → Krabi 3 → Koh Lanta 2. Boats, islands and very little driving. Fly into Phuket and out of Krabi to avoid backtracking.
This route is weather-dependent. From May to October, swap the Andaman for Koh Samui and the Gulf islands.
