Siem Reap to Hanoi?

Im planning on take a vacation sometime this month to Hanoi. I am new to Vietnam and I dont know which airline company can take me to Siem Reap and back. How much before flight I can book a flight? A month or two months in advance? And when it the cheapest to fly on this relation? I plan to go from Hanoi to Siem Reap and back!

You can normally book your flights up to eleven months before you depart. Cheapest time to fly down under is between April and June. It will cost you around 850 dollars as a maximum, and 700 dollars is minimal price for this flight. Cheapest airliner is Vietnam Airlines, so you should pick them if you have a chance. Have a good flight!