If you have not already booked your flight to Phuket then go straight to Ao Nang, Krabi and base yourself there.
airasia.com fly to Krabi and Ao Nang is only 35 mins from airport.
It is cheaper, scenerey is more stunning , easy access to other Islands such as Phi Phi.
Phuket is now getting over priced, over crowded and over rated.
Check out agoda.com for cheap hotels and tripadvisor for what to see and do.
I think its always best to book your rooms in advance as you might end up where you do not want to be - agoda do good rates
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