Try this thread regarding transfer times
http://www.phuket-info.com/forums/showthread.php?t=6934
I asked a similar question regarding transfer times - here is the answer I got from Diz
If you arrive at 19.55 and then try for the 21.oo that you mention, then I think you are cutting it very fine. Unfortunately you have to rely on circumstances a lot, one day you might be lucky, then next day not so lucky.
1. Fill in your Entry/Exit card on the plane.
Lucky day : you remember a pen.
Unlucky day : you forget pen and cannot find anyone nearby who has one, find pen and then it runs out !!
2. Immigration.
Lucky day : gate is close, plenty of desks open with little or no queue.
Unlucky day : you are miles away !! After walking for what seems like forever, you get there and there are only a few desks open and the queues are long.
3. Baggage Reclaim
Lucky day : suitcases on belt going round as you ge there.
Unlucky day : you see lots of passengers from your flight taking cases off, but no sign of yours.
4. Customs
Lucky day : breeze through !!
Unlucky day : get stopped !!
5. Getting to Domestic Terminal
Lucky day : get outside and straight on to special bus service which leaves straight away.
Unlucky day : no sign of bus so you walk, using connecting walkway (about 1/2 mile).
6. Domestic check-in
Lucky day : jump off bus and go straight up to check-in desk with no queue.
Unlucky day : arrived knackered from walking all that way with case and even though there is air-con, you are still sweating buckets !! Long queue at check-in.
7. Take off
Lucky day : take off is delayed by about 10/15 minutes, just enough to give you a bit extra time, but not enough to mean you get to Phuket late - job well done !!
Unlucky day : plane takes off on time, you're somewhere in the terminal and not on board
So what's your luck like normally ??
Cheers
Diz