The Phi Phi Islands in Thailand are absolutely gorgeous... rivaling Santorini for the most beautiful place I've been to date. Phi Phi is made up of two separate islands, Ko Phi Phi Don and Ko Phi Phi Le. Often times, the islands are thought of as one, since they are both tiny and are very close together.
The island that you'd stay on is Ko Phi Phi Don, but when talking about this island, it's typically just referred to as "Ko Phi Phi," which is pronounced "ko pee pee." It's about a 1 x 2 mile island in size, with no roads or cars on the island. You get around by long tail boats which are super old fashion (like a lot of the island) and part of the magic of the island's beauty. You can get to the Phi Phi Islands on a ~2 hour ferry ride from either Krabi or Phuket.
You can rent a long tail boat for pretty cheap to take you anywhere on the island. We stayed on the eastern side of the island, relatively close to the port in theory but on the complete opposite side of the island. To get there, it took about 20-30 minutes by boat and was a beautiful ride! The eastern side of the island is much more quiet and relaxing, as the west (near the port) is known to be the party side. It's a lot of fun, but you'll also find a lot of college aged tourists raging here. If you want to party one day, check out Bob's Sailing Booze Cruise. This side, however, is very overcrowded and kind of dirty in my opinion. So, as this trip was a leg of our honeymoon, we were happy to stay on the quiet side and take in the island's beauty. It's a much different world than the port area - clean blue water and a white sand paradise. Regardless of where you stay, it's very easy to get around
Our hotel was awesome. We stayed at Phi Phi Islands Village Beach Resort, which had the most beautiful grounds. With 2 infinity pools, 3 nice restaurants, and the most amazing (4 HOUR!) spa experience I've ever had, I was blown away. The service is great, and almost compares to our experience in Phuket! Being a remote island though, you can imagine that the interiors of the hotels aren't as modern as we found in Phuket. Regardless, the view of the hotel from the beach, with the lush green mountains in the background, was perfect. On the 2 days it rained while we were here, they drove all the guests around in golf carts. We had a wonderful time staying at the Phi Phi Islands Village Beach Resort!
One day on the island, we hiked through the forest to the very top of the hills, which had the most amazing view of the port and crystal clear waters! I highly recommend this pretty hike. It's moderately steep but only takes about an hour to get up. When you get to the top, you'll find a bar/restaurant and deck to hang out on too!
There are a lot of water activities to do on the Phi Phi islands, including diving, snorkel trips to Maya Bay, kayaking, boating, etc. There are plenty of bars, restaurants and shops to wander into and enjoy too!
As for day trips, you can easily rent a speedboat for ~$80 for 2 hours, or take a long tail (boat taxi) for much cheaper but takes longer. Maya Bay where the movie "The Beach" starring Leonardo DiCaprio was filmed, is a famous place to go. It's absolutely beautiful, but the crowds of tourists create a lot of harm to it's environment. There is a lot of garbage on the beach. It's great to get out and snag a photo, as it's definitely one of the most beautiful places I have ever been, but I wouldn't waste my time trying to snorkel there. Instead, head just on another side of the island to Pileh Bay, which is absolutely GORGEOUS, much less crowded, and so clean! From Phi Phi, you can also do day trips via boat to James Bond Island or visit Monkey Beach (which is actually on Ko Phi Phi Don itself).
If you visit Thailand, you'll have a wonderful time during any time of the year, but keep in mind their "summer" season is during our winter in the states. However, we technically went during their rainy season (our summer/fall), and got sunshine most days! You really can't go wrong at any time in the year!
Next, check out my Singapore travel guide - it's a great city for foodies and urban adventurers!