Island hopping in Thailandshow island map of Thailand --- find flights --- book a room with booking.com*
Island hopping is easily possible in Thailand. There are five regions, where you may hop from island to island. But mostly these trips are limited to the season from November till May, due to bad weather conditions in the rainy season.
From Phuket to Krabi: flight to Phuket (with Airasia, Nokair, Bangkokair), by boat to Koh Yao, Koh Phi Phi, Koh Lanta and Koh Jum. Then by boat or Minibus to Krabi and flight back to Bangkok.
Koh Samui - Koh Tao: flight to Koh Samui (Bangkokair), boat to Koh Phangan and daytrip to the Angthong Nationalpark (also possible from Samui). Boat to Koh Tao and to the mainland to Chumphon. Then Bus to Bangkok (see Lomphraya).
Trang-Islands: flight to Trang with Airasia or Nok-Air. From Trang to Palian/Youngstar by Taxi or Minibus. Boat to Koh Sukorn, to Koh Libong and Koh Mook by longtail and speedboat and Koh Ngai and Koh Kradan by speedboat. Then back to the mainland to Pak Meng and Trang.
South Thailand: flight to Trang or Hat Yai (Airasia, Nokair, LionairThai). Taxi or Minibus to Pak Bara, then boat to Koh Bulon, to Koh Tarutao and Koh Lipe. From Koh Lipe daytrips to Koh Adang or Koh Tong. By speedboat north to Koh Mook, Koh Kradan, Koh Ngai, Koh Lanta and flight back to Bangkok from Krabi, Trang or Phuket.
Alternative option: start the trip from Langkawi (Malaysia)
Eastern Thailand: Flight with Bangkokair to Trat. Boat to Koh Kood, Koh Mak and Koh Chang. Daytrips to Koh Wai and Koh Kham. From Koh Chang back to Trat.
Also: Bangkokair offers daily flights from Pattaya/U Tapao to Koh Samui and Phuket.