QUOTE(travelingdiva @ Aug 19 2010, 07:05 AM)

Hi,
I hate to be the bearer of bad news but you may want to take a look at a map of Thailand. Samui is in the Gulf of Thailand, near the east coast whereas Phi Phi is in the Andaman Sea, near the west coast. Due to that fact, I would say the best option is to fly from Samui to Phuket and from there you can catch a boat to Phi Phi. The other option is to boat from Samui to Surat Thani, then take the bus to Phuket, then another boat to Phi Phi.
Good luck!