tafkasnyc:
I just got back this week from a 5-day trip on the Mermaid I to Mergui and Burma Banks (my first time up that way). Swam with mantas! To go up there you definitely need a liveaboard. Only about six boats go to Myanmar, and they all operate out of Thailand, so if that's what you want, you need to check the dates and go on the boat that fits your availabilty best. One great thing about Myanmar is that you won't see other divers at all.
If you want the Similans, it's possible to do day trips with a couple of operators (South Siam used to do it, but I've heard they don't anymore), however, it's a long boat ride out, and I prefer a liveaboard for the Similans. The Similans are generally swarming with divers, but not this season since the tsunami scared the tourists away, so it's a good time to visit.
Another option for a short liveaboard from Phuket is the southern islands, Hin Daeng and Hin Muang and Koh Ha--which I did on the Mermaid II as a two-day trip (8 dives)--you can do these as day trips from Krabi, too, and whale sharks have just been seen in the area!
Day trips from Phuket also work. I liked Sea Bee's boat Excalibur since it's fast and you get three dives on a day trip instead of the usual two on most other boats.
