The area of Mai Khao is great. Very nice hotels, very quiet and you still have access to everything that you might be interested in in Phuket, including the airport which is only 15 minutes away. And the Phuket airport has more options than Krabi or Chiangmai Mai (generally).
I haven’t been to either Krabi or Chiang Mai, so I can’t make perfect comparisons, but Phuket Island can be a great destination if you avoid the Phuket Beach area.