Flight Suvarnabhumi Airport departs from Bangkok Suvarnabhumi Airport at 16:45 and arrives at Shenzhen Shenzhen Bao'an International Airport at 21:20.
The flighttime is about 3h 35m. The distance travelled ("as the bird flies"): 1477 Km. So the average speed is roughly 412 Km.
There is an 1 hour time difference between Bangkok and Shenzhen