Writing this from Hue, overlooking Perfume River.
If it is just two month left, than prices unlike to go down and most likely will go up, based on my experiences with intra-Vietnam flights.
For cheap flighs with VN one should book flights at least 6 month before departure if you want to catch their Eco fares. The same applies for VietJet. You can sign up for their fare newsletter to know when is time to book.
Alternatively/in addition you can setup fare search at Skyscanner with target prices but, unlikely you get great deal right now two month before departure.
Three words of advice:
1. If you have connecting flights with separate tickets make sure you have at least 4h between flights. Not a single time my intra-Vietnam flights departed on the time shown when I booked them. Even with VN within 2 month of departure time flight moved three times forward and back. At least VN notifies you via email, Jetstar and VietJet - do not, unless you sign up for paid notification service (not a joke).
2. Avoid booking the very first and last flights - they are cancelled most often.
3. Check traffic conditions on the date/time of the departure - in Saigon it might take 45min to travel 5km via car.
Last edited by invisible; May 8, 2018 at 10:27 am