I'm a long-time lurker who wants to give back after snagging travel deals plenty of times on this wonderful website.
Jetstar have very cheap return flights from Hamilton to Ho Chi Minh City (AKA Saigon), via Sydney, from May to September 2027.
For example, return flights from 8 August - 26 August 2027 are $580.98. You can find other, similar fares across those months on the Jetstar website (or Google flights / kiwi.com).
Club Jetstar brings that example fare down further to $520. While the subscription costs $65 per year - might not be worth it if you're going solo - if more than one person is travelling, it's definitely worth considering. This can be done in the checkout process. Just make sure you cancel your subscription after you sign up.
Note that Jetstar are introducing Ryan Air-style restrictive carry-on rules, where you can only bring a small backpack as part of the base ticket price, in February 2027. In my case, it cost an extra $120 per person to have regular carry on allowances for all the flights (with the additional Club Jetstar discount).
This might be a pricing error, but I have had my eyes on this for a few weeks and finally purchased tickets today, which suggests that might not be the case. In any case I'd suggest buying sooner rather than later. The way fuel prices are going, it's likely we won't see these kinds of prices again.
At a price like this, it's worth driving from Auckland or even Wellington / anywhere else in the North Island. And it's a particularly good deal for anyone who has the misfortune of living in Hamilton.
Apologies in advance if I have made any errors or faux pas - this is my first and likely last post.