Thailand forum

Greetings all! I am heading to Thailand for my first visit to SE asia from March 26 - April 20. I am going with 2 friends, and we want to party, scuba, and see as much as we can, basically. We have some of this hashed out, but are unsure about some of the trip. Just hoping to score a little advice. Here goes....

March 26 - arrive at BKK early in the morning
27 - BKK
28 - Travel to cambodia
29 - Cambodia (Angkor wat/ Siem Reap)
30 - Cambodia
31 - Cambodia
April 1 - Cambodia - BKK
2 - BKK - Koh Samui (Flight already bought)
3 - 7 - Koh Phangan for hanging out and FMP
8 - Fly to Phuket
9 - 12 - scuba in similan islands, check out phi phi, maybe phuket for a day
13 - fly to Chiang Mai for Songkran
14 - 16 - Enjoy CM
17 - Fly back to BKK
18 - night in BKK
19 - Fly back late at night

So, my main concern is that this is putting way too much in to one schedule, and trying to fly to CM in the middle of Songkran. Since it is such a big holiday, it seems like it will be pretty hectic to travel during that time. The other option we have is to check out CM in the Cambodia slot at the beginning of the trip, and stay in Phuket for songkran. Then we would have to miss out on Cambodia completely. All suggestions welcome! Thanks!