Option 1: Bangkok + the north
Bangkok 3 nights (old city, river, one day trip) then Chiang Mai 3 nights (Doi Suthep, an elephant sanctuary, one free day). No beach, but the most variety per day.
Option 2: Bangkok + one coast
Bangkok 2 nights, then Phuket or Krabi for 4. One internal flight, one hotel change, and enough beach time to actually relax.
Option 3: the Gulf only
Fly straight to Samui, stay 6 nights, do Ang Thong and one other boat day. The lowest-stress version, and the best for families with small children.
The mistake
Three islands in seven days. Every transfer costs half a day, and you spend the week packing.
