Are the ATMs at banks inside this airport safe to use?
Yes, all of them.
Can anyone recommend a specific one?
No, they're all OK - you'll find a couple together in the right hand part of the arrivals bit. PHO and (I think) WBK. Both fine to use, however I use PKO since if you put an odd number in (say, 490 instead of 500) you'll get smaller denomination notes, useful for change.