I'm thinking of staying on Koh Lanta at Primali or on Koh Phi Phi at Phi Phi Island Village or Holiday Inn for 4 nights. Any suggestions? Also, what is the best way to travel to and from above islands from Bangkok airport?

I can's speak of the Phi Phi Island Village or Holiday Inn, but the Pimalai on Koh Lanta is fantastic, with it's own beach. Very innovative landscaping and architecture, unforgettable. It's very quiet there, however, so if you want nightlife you'll have to make your way a bit further north along the coast to where more resorts are located.

Best way to travel:

Morning flight from BKK to Krabi Airport, then a minibus into town to the dock where the ferry leaves for the islands. I think the first one leaves at 10:30. The trip takes about 2.5 hours.

I forgot to mention that we love to snorkel and hope to be somewhere where the reefs are healthy and the fish abundant.

On Koh Lanta Pimalai or Sri Lanta, as brother said, get an early flight.
On Phi Phi the Holiday Inn is nice but you might want to take a look at Charlie resort, now this is rustic and basic, but has a/con huts, clean, good atmosphere and they are into all the water activities, it's not a lux place but for a couple of days on a tropical island it's nice for a change to stay in a hut (yet, have a/con etc ). If you are into having a snorkel maybe Phi Phi should be your choice.

Try these 2

www.freewebs.com/koh_samui_hotels/kohlanta.htm

www.freewebs.com/koh_samui_hotels/krabi.htm ( for Phi Phi accommodations )

Do take a look at both the Holiday Inn and then at Charlies resort and it gives you the difference and the perspective on Phi Phi

We stayed at Phi Phi Island Village about 5 years ago - very lovely and secluded. The downside is that you must take a boat to get anywhere.
The snorkeling is better from Phi Phi than Ko Lanta, although Ko Lanta is more affordable, has more to do, and has more "culture".

Any resort on Koh Lanta can set you up with a great snorkelling excursion out to the karsts. Food and water are included usually as well as a stop at the Emerald Cave. Good Fun and very inexpensive for a 6 hour tour.

For what it's worth, my wife and I didn't think the snorkeling in Phi Phi was particularly good. The best aspect was that the coral formations are large and the water was very clear. But there was no color to the coral and the fish were not abundant. We didn't do any other snorkeling in Thailand, so our reaction is due to relatively limited comparisons with snorkeling in Aruba, Kawaii, Cancun, and French Polynesia.

Scteach - what time of year? Phi Phi area is 'out' for any decent snorkeling end April thru to end October, if you were thinking of that time of year you need to look at the Gulf area e.g Koh Tao for snorkeling though you can also base yourtself on Koh Samui and then take the snorkel trips from there, time if year really dictates which 'side' to go for.

Thank you, James. We will be on Phi Phi or somewhere similar the first week of February next year. What will be the best snorkeling at that time?