If his/her bags are tagged through, he can easily get QF boarding passes from the (airside) international transit desk at Auckland - show them the bag tags from RAR and off you go. No need to enter New Zealand. Transit in Auckland is easy peasy.
Not too sure about this these days.... IF your bags are tagged is the big question. Mrs TiggerK was recently chatting to SYD airport staff about this exact kind of scenario. In days of old, it probably wouldn't have been an issue, but with the current security situation, airlines will generally not allow baggage to be through-checked without you having been checked in and holding a boarding pass for your onward flight, no matter who the next carrier is. Basically if AirNZ at RAR check your bags through to BKK without you being actually checked in for the AKL-SYD-BKK sectors, then there seems to be nothing in the system at AKL monitoring that the owner of that bag has boarded their QF aircraft, and obviously the bag cannot fly alone.
I suspect you'll have to get bags, go into NZ and back out again via QF. Can be a busy time at AKL around then, but I expect you'd still make it.
I hope someone says I'm wrong for your sake. I know there will be situations where they certainly allow this kind of thing.... But Shanghai and LAX for example do not, ALL customers must collect bags and go through customs, but in AKL I'm not 100% certain, hopefully YMMV.
Cheers
TiggerK