I'm looking at doing a visa run next month to activate a second tourist visa.I was looking at flying to Phnom Penh or Penang and coming back straight away on the same aircraft.I know it could be a bit risky,but if I'm already checked in for the return flight and have my boarding pass printed,would it be possible.I've never been in either of these airports so I'm not familiar with immigration or the size of the airport.

Check your chosen carriers turnaround time AND their minimum check-in time. For example, AirAsia don't hang about but their check-in closes 1 hour before departure and having a pre-printed boarding pass won't change that.

I can't speak for the two airports the OP mentions but I have done the fast turnaround in Kuala Lumpur (the real airport at KUL and not the LCCT). Nice airport to kill a couple of hours at.

Penang is quick but agree withe post above, don't even think about it with AA, if the incoming flight is late (not uncommon) and they try to turn around quicker then your screwed, point to point carrier.

Dont' try it at Phnom Penh...Air Asia is never on the ground more than 45 minutes before they fly back to Bangkok, you'd miss check-in time for sure.

you are farang/ it wont work that way:

1. Air Asia is based at PNG-its not a turnaround there-its in BKK

2.you MUST show to have been in another country when returning-this means stamps+ for Camb the visa=20US$PLUS the Camb airporttax=25 US$-forfeiting any apparent low price

Best choice after all is to use Air Asia to KUL/LCC(about to move in the next weeks!!) and come back on a flte back 2-3 hrs later-this gives you much more choice in low fares. BOTh THai AA and the original Malay AA ply this route- up to 8 times/day

KL LCCT is not bad to get around in and rather small. But does does have some good facilities for a few hour lay over. Also, no visa fees.