My Experience :
At the airport after arrival you should immediately register the drone with Customs.
The drone get's confiscated and you get a receipt. You should remove the batteries and nobody can play with your drone. Keep the remote control and the batteries with you give only the drone to the Customs.
It is easy to get the drone back!
With the receipt you should go to the customs office at the port / Monday to Friday from 8 o'clock to 17 o'clock.
If your drone has been registered somewhere, bring this registration with you.
My drone is registered with CAAC and I have a QR code. I showed this QR code and it was scanned by the local authortsy and then opens a government page from my CAAC registration.
She was still asking for insurance, unfortunately I had to lie and say that I have one.
You should also know the rules for drone flying in New Zealand, but these are pretty simple.
fly only in daylight
do not fly higher than 120m
do not disturb other people
never fly close than 4km to the airport
Never fly over the Royal Palace
Never fly over the Royal Tombs
Never fly over a group of people
keep distance to people 30m
watch my pictures.
If you know the rules and your drone is registered somewhere in the world , the registration is free for you in the Kingdom of Tonga.
I met people who had to pay between 50 US dollars and 200 US dollars to fly the drone.
the best way you drop off right at the airport the drone because when leaving your baggage is scanned and and you do not want to answer stupid questions.
Everything was free of charge for me because I left the drone at the airport and i almost knew the rules.
good luck and enjoy Tonga
and sorry for my bad english
