4 countries in 10 days is too much. 3 countries would be more comfortable. Keep in mind you will be flying almost every other day. I'm assuming (really I'm just hoping) that you have been to Asia many times and know a little bit of the language and how to get around. Otherwise, if this is your first trip to Asia, then yeah, focus on one or two places.

So assuming your comfortable cramming in as much as possible, here's what I can suggest.

Fly into HCMC or Hanoi. Spend that day plus the next day walking around the city. Possible Mekong Delta day trip if you're in HCMC.
Fly to Yangon. Spend that day plus the next day walking around the city. See the Shwedagon pagoda.
Fly to Bangkok. Spend that day plus the next day walking around the city. Royal Palace and Wat Po (should be open by Dec 1???)
(I've never been to Indonesia) Fly to Bali. Spend that day plus the next day walking around and enjoying a beach.
Fly back to Australia.

That leaves you an extra day or two to add somewhere.
With such a tight trip, you should get all your visas in advance. I'm an American, so I need a visa for Vietnam and Myanmar. Don't get sick. Book all your intra-Asia flights in advance. Might as well book your hotels in advance. Pack very light, 2 pants, 2 shorts, 5 shirts, some underwear, sandals. Make lots of documentation on the cloud and keep offline versions on your devices. If you're on a tight budget use Air Asia, and bring cash to avoid ATM fees.

Do-able, but BUSY. Don't do it You probably won't enjoy it that much.

I should add, I have done itineraries like this before. They are more like a scouting trip to see where I want to spend more time in the future.