We had a flight from Bangkok into Phuket. We picked up our rental car and drove north to Khao Lak. Stayed at Le Meridien. This was a time for my husband to scuba dive and for us to relax at the beach and the pool. We also spent time at the town market and visited the Tsunami Memorial.
I've detailed our time with pictures attached in the form of a blog. Thailand entries are under March. Just go down to the dates and click for Khao Lak. We really liked this place as its low key vibe was just what we needed after 2 months busy sightseeing/traveling in SE Asia.