Flight Phuket → Bangkok (1h25, last connection to international flight, or Bangkok night then flight)
Alternative: direct flight Phuket → international (Air France, Qatar, etc.) skipping Bangkok
If your international flight leaves from Bangkok, plan 2 nights in Bangkok at the end instead of 1 transit day. Same total duration, much less stressful. BKK→Phuket flight can be cancelled/delayed in monsoon.
Day 3-4: Krabi limestone islands
Budget by profile for 7 days (per person, ex-international flights)
Backpacker (12,000-18,000 THB)
Hotels: dorms/guesthouses 400-700 THB/night
Food: street food + markets, 250-400 THB/day
Transport: ferries + bus, 2,500 THB total
Excursions: shared 4 Islands 1,200 THB + shared Maya Bay 1,500 THB + park fee 400 THB
Total ~12,000 THB very tight, 18,000 THB more comfortable
Mid comfort (25,000-40,000 THB)
Hotels: 3* mid-range 2,500-4,000 THB/night
Food: street food mix + sit-down restaurants 800-1,200 THB/day
Transport: domestic flights + private transfers
Excursions: speedboat Maya Bay + Krabi Hong Islands + Bangkok floating market
A few massages and bonus activities
Upscale (60,000-100,000 THB)
Hotels: 4-5* 6,000-12,000 THB/night
Food: upscale restaurants, dinner cruise, fine dining
Yes for a well-aimed first time: Bangkok culture + South islands. You will not see the North (Chiang Mai), no Pai, no Sukhothai, no Golden Triangle, count 12-14 days to add the North. But a well-built 7-day trip beats a scattered longer one.
Bangkok at the start is better. You arrive jet-lagged, Bangkok absorbs the fatigue with its temples and energy. Islands at the end = you leave relaxed and tanned. The reverse works but jet lag hits hard on the beach.
1-2 days Bangkok max (Wat Pho, Chinatown, river dinner), 4 days Krabi/Ao Nang single base with hotel pool + 4 Islands Tour + elephant sanctuary day, 2 days Phi Phi day trip or overnight. Avoid multiple internal flights, tiring for little ones.
December-March (dry season). November = very good. April = hot but dry. Avoid July-October (south monsoon, unstable ferries). If you must travel in July, do Bangkok + Chiang Mai instead of South.