Video has emerged of a savage attack on an elderly British couple and their son while they were on holiday in Thailand earlier this month.
The family, who are reportedly from Scotland, were left motionless on the ground after the attack, which lasted two minutes, in a crowded street in the beach town of Hua Hin on the evening of April 13.
Thai police said all four of the suspected attackers had been arrested, identifying them as being aged in their twenties and thirties.
The disturbing footage shows the 43-year-old son of the family accidentally bumping into another man before the fight breaks out.
The severity of the subsequent attack has caused an outcry on social media with the video, which was captured by overhead security cameras, showing the family repeatedly punched and kicked even after they had been left lying on the ground.
The 65-year-old woman suffered serious eye and head injuries that caused a build-up of fluid in the brain and required an operation, according to Police Col. Chaiyakorn Sriladecho.
The father and son suffered head injuries requiring stitches.
Chaiyakorn said the men suspected attackers were sorry for their actions and that they had claimed to be drunk.
"We have now arrested all four suspects," he said. "Three of the men were arrested within days of the incident and the fourth on Thursday, he said, identifying them as in their 20s and 30s.
"The men say they are sorry and that they wouldn't have done this if they weren't drunk."
The incident is the latest blow for Thailand's image as a travel destination.
In March, four French tourists were assaulted on the island of Koh Kut as they walked to dinner. They included a mother and daughter who were both raped.
Two British backpackers were murdered on the island of Koh Tao in 2014. Autopsies showed the couple, a young man and woman, had been severely beaten and the woman raped. Two Myanmar migrants were convicted of the crime based on DNA evidence that rights groups say was questionable.