Can you get a visa on arrival in Vietnam traveling from Thailand on an Australian passport?

Myself and my Thai girlfriend are traveling from Bangkok to Da Nang Vietnam soon.Will we both need visas for this trip.

A little off topic. But anyone know if I can just fly to Vietnam from Thailand and get the visa on arrival without the invitation letter or i can get everything sorted out there? Tried the evisa but the website won’t let me get to the part where I pay for some reason .

Looking for some advice and hopefully not to much abuse, left Thailand on the 27th 4 days before my 30 days were up and went to Vietnam and have my flight back to the UK booked from Hanoi on the 9th of January cause I thought I’d stay but to cut a long story short didn’t like it so have decided to fly back to chiang Mai today I know I want have any problem coming back into Thailand but my question is, will I be ok to enter back into Vietnam for my flight home or is there some sort of limitations on how many times you can enter the country with in a certain time even though I could prove I’ve got a flight out the country a matter of hours later, hope you guys can help I understand it’s nothing to do with the Thai visa side of thing but there’s a few people in here with a wave of information and advice, sorry for the long post just tanned two litres of beer 🍺🍺

I will arrive Bangkok in the late evening from Rome.with flight to Vietnam next morning via viết airlines.Do I need Thai visa for overnight transit?