I've never been to the airport on Phuket and I have a question...

I'm planning a flight where I have to transfer in Phuket. I would arrive at 09:15 (Bangkok Air domestic flight from Samui) and then need to check-in for 10:40 Tiger Airways flight to Singapore (Samui-Singapore direct flights are full). I will only have one carry-on bag. Tiger's website says they close check-in 45 minutes before the flight so that would make it close at 09:55 leaving only 40 minutes (not 85 like the thread title says and assuming the flight is on time). Is this enough time to make the transfer?

Phuket airport is not so large and should take you about 10 or 15 minutes to exit the flight and get to the check-in desk, assuming domestic flight and no checked bags. In theory you should make your flight assuming your Samui flight arrives on time. But it will be very tight, best of luck.

With just one carry-on bag you should have no problem, given your Samui-flight is on time, and the chance for delays are not that big early morning. Phuket Airport is a small terminal. When you arrive domestic, pass the baggage claim area, then turn right and walk the stairs one floor up and you are in the departure hall ready to check in. Good luck.

your'e cutting it close. as you stated, any impediments concerning your connection you'll have to spend a night in Phuket.

(from my experience with BKK airways, they are pretty punctual on time schedule - but anything could happen)

It's like zulugut says, small terminal, very quick route from baggage carousel then up the stairs. DO NOT exit the terminal, go to the stairs at the far left as you exit from baggage. The stairs are small and very obscure; there is a small desk in an alcove at the foot of the stairs so it looks like a dead end. Just go up the narrow stairway which leads directly into the departure check-in area. Tiger counter is about the middle of the departure row.

Assuming on-time arrival should be no problem; the Phuket baggage arrival is usually very prompt.