(From Scott's Cheap Flights)
full-service fares to Vietnam.
If you're starting in Sydney, an open-jaw ticket might be a good option if you'd like to fly into Ho Chi Minh City and return from Hanoi for about the same price.
No bag fees, etc.
FROM: Melbourne (MEL)
Ho Chi Minh City (SGN) - $686*
FROM: Sydney (SYD)
Hanoi (HAN) - $696*
Ho Chi Minh City (SGN) - $696*
( * nonstop / direct)
WHEN: October to November 2019 and February to June 2020
NORMAL PRICE: $900 for full-service nonstop
AIRLINE(S): Vietnam
BUY BY: We think these fares will last 1-2 days
To find the cheapest available dates, search in Google Flights first, then look on another OTA like Momondo (linked).
Great place to visit.
For people looking for travel ideas, I recommend this 10 day tour. I did this the last time we went back to Vietnam and it was great. The one night stay in Halong Bay is well worth the price.