That's a lot of travelling in 10 days. If you want to go to the full moon party. I would just keep my trip to Bangkok and Samui/ ko phan gan. It is a wonderful time of year to be in Samui. I would soak it up and spend as much time there as possible. If the full moon thing isn't compulsory, you could do Phuket/Phi Phi instead but I wouldn't attempt both as the travell between will eat up too much of your precious time. I am posting a travel report on fodors dot com in the asia forum of our time in Phi Phi and Ao nang earlier this month. I will spend some time going into Phi Phi in detail if you care to have a look.

__________________
I love Thailand this much