The carrier is adding an additional flight to and from Ho Chi Minh City.
From October 25 it will operate a total of six non-stop flights per week - three each to Hanoi and Ho Chi Minh City.
All services are now being operated by the 787-9 Dreamliner.
Return fares from Heathrow to Ho Chi Minh City and Hanoi currently start from £400 or £430pp respectively, inclusive of taxes.