Diverted pretty abruptly 90 degrees to CNS which suggests something more sudden than deciding they needed fuel.
https://www.flightradar24.com/data/a...k-nzh#23d97463
https://flightaware.com/live/flight/...320Z/RKSI/YBCS
Medical emergency would seem most likely given they were on their way again in an hour or so.
https://www.flightradar24.com/data/a...k-nzh#23daf7f0