Upvote:4
Neither Australia nor PNG authorities technically have key access to TSA locks. However both can and will physically search luggage if they have cause to do so, usually because of an anomaly sighted on other scanning.
If you have locked your luggage that physical searching could be done by removal of the lock, either via keys or more destructive means, or alternate access, e.g. cutting open the bag. It's not unusual for locks to be removed and not replaced on Australian flights.
Cable ties or destructive clips are other options if you want to reduce the likelihood of your bag being damaged while also "proving" that your bag has been tampered with.