A drunk passenger instantly regretted starting a fight with another traveller, who turned out to be an amateur boxer.

The local in a red shirt allegedly mocked another commuter, former Muay Thai fighter Rattharin, 27, who was sitting behind him on a moving ferry.

Footage shows the intoxicated traveller standing on his seat at the front section of the boat, shouting and gesturing at the retired sportsman in Samut Prakan, Thailand, on October 23.

Moments later, the two began exchanging punches. Rattharin landed several clean hits, sending his opponent reeling as their girlfriends screamed and tried to break up the fight.

Rattharin grabbed him by the shirt and punched him in the face several times. The intoxicated man struggled to fight back as his trousers slipped down during the scuffle.

Boat worker Rewadee, 59, said: ‘We picked up passengers from Phra Samut Chedi Pier going to Samut Prakan Pier. 

‘During the journey, the passengers started fighting, ignoring others' attempts to intervene.'

Several passengers were caught in the chaos due to the cramped space and tried to move aside to avoid being hit.

The scuffle only ended when the driver steered to a riverbank to get help from a security guard who dispersed the brawlers.

Retired boxer Rattharin later said: ‘At first, I thought he was just insulting some foreigners visiting the festival, so I did not pay much attention. But he kept shouting louder and louder.

‘I was sitting at the back of the boat, which was already crowded, until the fight broke out and everyone started standing up.

‘The boat operator tried to turn back and drop him off, but since we were already in the middle of the river, he just gave a warning instead.'

Despite the mass brawl, no one filed a complaint at Mueang Samut Prakan or Phra Samut Chedi police stations.