Flight Tan Son Nhat International Airport departs from Ho Chi Minh City Tan Son Nhat International Airport at 23:45 and arrives at Seoul Incheon International Airport at 06:30.
The flighttime is about 4h 45m. The distance travelled ("as the bird flies"): 2519 Km. So the average speed is roughly 530 Km.
There is an 2 hour time difference between Ho Chi Minh City and Seoul