No, not at all. The motorist behind lightly tapped his horn after the light had turned green. Entirely appropriate.
Yes, the motorcyclist "should" have looked both ways in a country as with roadways and intersections as lethal as Thailand, but in any normal country, would not have any reason to do so.
What I do find bizarre, though it may have been outside of the dashcam viewing frame, is that NO ONE stopped to run to the motorcyclist who had been hit to his assistance or acertain his level of injury or mortality - not the pedestrian, not the driver of the dashcam car (who simply proceeded on his way forward), not other cars passing through the intersection.
Is that how mundane traffic accidents and death has become in Thailand? ????