This happened on, 24 Aug 2016 around 745AM along KPE towards ECP at Buangkok Drive entrance. The driver was caught showing middle finger to the driver of the Hyundai Avante driver.
It is not clear what has happened that provoked the driver of the BMW. Maybe the driver or drivers had been in a bad incident before this.
I think it is not really necessary to show rude gestures like this to others. Use the horn to warn the other party instead might place both parties in a better situation for a better day ahead.
The video is too big to upload here. You may wish to get it here.