Three members of a British family were punched and kicked unconscious during an attack in a Thai tourist resort.
The holidaymakers, including a woman, were left needing hospital treatment after the vicious assault by a gang in Hua Hin during celebrations for the Thai New Year, it is understood.
Six people are said to have been arrested in connection with the incident in the popular coastal destination on April 13.
The Britons, who are understood to be middle-aged, have since been released from hospital.
CCTV footage released by local police to try and track down the suspects shows a brief argument before the attackers punch and kick the victims.
Both men suffer blows to the face and body, and when the woman who was initially knocked flat out by a punch sits up, one attacker delivers a kick to her head.
The images show all three being beaten unconscious and left on the pavement, as a large crowd watches the unfolding scene of assault on the busy street.
The Songkran New Year celebrations are also known as the Water Festival, when Thai families splash water on each other as part of a religious ritual of renewal.
The British Embassy launched its #SongkranSafe campaign ahead of the festivities and encouraged holidaymakers to take part while appreciating local customs and traditions.
In the past tourists have been arrested for breaching decency laws by taking part without wearing T-shirts.
A spokeswoman for the Foreign and Commonwealth Office (FCO) said: "Our staff have been in contact with the family to offer assistance and will remain in contact with the local authorities."
The FCO said they had no information on the condition of the three UK nationals following the attack.
In the video a passer-by appears to come under attack from several men after trying to intervene in the melee.
A contributor to the Hua Hin internet forum said they had rushed to the help the family who they recognised from a nearby bar. As revellers were leaving for the night groups of Thai youths had gathered on the street looking for trouble.
They wrote: "Within 20-30 metres of leaving the bar the Thais were punching the 65-year-old lady in the face!! The elderly gentleman was down on the floor and their son was beaten very badly!!!
"At this point I caught up to the scene and pushed one of the youths away from the woman...
"I got severely punched and kicked for my troubles, but felt the need to protect this frail lady.
"The three of them are still hospitalised and I will need cosmetic dental work done."
According to the account, "gangs of Thai youths were priming themselves to start punching Westerners" in the area before the attack.
"Not one person (other than myself) came to aid these old folk and they ended up laid in the road bleeding."