We just spent 9 days in the Thai islands and it was glorious! The first few days were spent in Krabi. We splurged on the hotel and stayed at a very nice one. It was well worth it! In the islands everything is limestone cliffs and it is beautiful! Very similar to Hawaii (mountains and greenery). These areas were hit pretty hard by the 2004 Tsunami. You can still see remnants of the disaster, but overall they have gotten back to normal. We spent our first day kayaking and hanging around the hotel.
In the islands you take boats everywhere! Longtail boats are cheaper and in our preference more authentic. Basically we just rented a private longtail for the day when we wanted to do something (pretty cheap and comes with a driver). They have a plethora of islands to choose from, each with their own charm. The first one we went to was Railay Beach. This beach is very popular for rock climbing and is considered some of the best in the world. The water everywhere is a ridiculous green/blue and coral reefs are in abundance!
And the best part is, you can get a foot scrub and massage on the beach! Ummmmm yes please!!
The next day we took a longtail to Hong Island. The snorkeling here was great!
And on our last day we did a 4 island tour on a speed boat: a cave in Railay, Chicken island, Poda island and Tup island. Again, the snorkeling was awesome!
The islands have been good to us! More to come soon!
Two Wayfaring Wanderers 
your trip just keeps getting better and better…Did you guys use the plethora in a sentence?