Do I need a visa in Vietnam if I only stay for less than 15 Days.

I will be travelling from Bangkok with my Thai wife to Ho Chi Minh City on Thursday 5 January 2017 by Air Asia flight for holidays. I have an Australian Pass Port. I will be leaving on the 16 January 2017 back to Bangkok with AirAsia. I understand I do not require a visa now on short visits but I need confirmation of this and / or procedures if I require a visa and if this can be obtained at such short notice at Ho Chi Minh city airport.
Thank you look forward to receiving your reply.