I am trying to book the following flights online. I have tried entering the information various ways but I am only able to piece this together as three different tickets. Even if I try "multiple destinations" it won't work. Must I call United to get all these flights on one record locator? I am trying to fly in business or F:

BKK-SYD on 11/29
CHC-BKK on 12/18 (via AKL)
BKK-JFK on 12/19 don't care where I connect

Thanks,
Moe