Air Asia is one of the few discounted airlines in Southeast Asia and it offers many daily direct flights from Bangkok, Kuala Lumpur and Jakarta to Vietnam. On the route from Kuala Lumpur to Hanoi, there is a daily flight with the departure time of around 6:25 a.m. The fare for these flights is pretty low with 249 USD for the round trip and 128 USD for one way trip.
Moreover, Air Asia offers another daily flight from Bangkok to Hanoi. The take-off time of this flight is 6:45 (local time) and the price for ticket hovers around 72 USD for one way trip and about 144 USD for round trip.
There are more daily flights to Ho Chi Minh City than Hanoi, with two from Bangkok, one from Jakarta and three from Kuala Lumpur on a daily basis. The flights from Bangkok departs at 7.45 and 15.55 every day, and the fare for these flights is approximately 128 USD for round trip and 48 or 68 USD for one-way trip.
On the route from Kuala Lumpur to Ho Chi Minh City, Air Asia is exploiting three flights at 9.10, 14.55 and 18.20. The fare for those flights is about 73 USD for one way trip and 146 USD for round trip. Moreover, Air Asia has a direct flight from Jakarta to Ho Chi Minh city that departs at 16.35 (local time) with the average fare of 92.7 USD for one way trip and 185.4 USD for a round trip.