This disturbing footage shows the moment a man reaches around a bus chair to try and touch a female passenger.
Panida Chianchana, 24, was travelling on a public bus in Bangkok, Thailand, when she felt fingers on her chest.
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The university student said she was touched ''two or three more times'' before she decided to record it.
Footage of the incident shows fingers probing the area where her waist had been before leaning forward.
Panida bravely confronted the wide-brimmed hat-wearing ''psycho'' to ask him ''Why did you put your hand there? Why did you touch me? Are you a psycho?''
After going public with the assault, several more women came forward to say they had been groped by the same man, an airport worker, who was later arrested and confessed.
Panida - who waived her anonymity - said: "I was taking the bus from Chatuchak to the Victory Monument and thought to myself 'what's wrong with my chest?'. There was a strange feeling that there was something pressing inwards, like the shoulder strap.
"But it happened two or three times more so I decided to turn on the phone to record it. I saw a hand try to get through from behind the chair and reach my chest. So then I stood up and asked why he was doing this. I said 'are you a psycho'?
"The man denied that he had done anything wrong and rushed off of the bus.
"The other passengers did not help at all. They just sat quietly together.''
The man, named by police as Peerapol Yodcharoen, 36, is reportedly a worker at the busy Don Muang Airport used by millions of tourists. He was later arrested and confessed.