Flight Haneda Airport departs from Tokyo Haneda Airport at 02:00 and arrives at Ho Chi Minh City Tan Son Nhat International Airport at 06:10.
The flighttime is about 6h 10m. The distance travelled ("as the bird flies"): 3910 Km. So the average speed is roughly 634 Km.
There is an 2 hour time difference between Tokyo and Ho Chi Minh City