Driver flashes high beam at car after being overtaken -- but who is in the wrong here?

Stomper Andy alerted Stomp to a video of a driver who was driving in the rightmost lane in a tunnel and then started flashing his high beam at another driver who later overtook him.

The video of the incident was posted on Roads.sg's website.

Said Andy:

"I came across a video showing a road hog who hogged the road and caused others to overtake him.

"After which, as shown in the video, he high beamed whoever overtook him. 

"Really ugly attitude and the driver must have a problematic character."

However, to be fair, the driver who overtook the silver car appeared to be travelling at a speed faster than the rest of the vehicles in the tunnel, and it is unclear if he had driven over the speed limit.

Who is in the wrong here?

Watch the video below.