A Welsh family have been punched and kicked unconscious during an attack in a tourist resort in Thailand.

The holidaymakers, believed to be a 65-year-old woman, a 68-year-old man and their 43-year-old son, needed hospital treatment after the vicious assault by a gang in Hua Hin during celebrations for the Thai New Year.

Police said three alleged attackers have been arrested and one more is being sought in connection with the brawl in the popular coastal destination on April 13. All are Thai.

CCTV footage leaked online shows a brief argument taking place 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 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 in the busy street.

Police spokesman Chaiyakorn Sriladecho said the attack started after "the son accidentally bumped into one of the Thai men".

He said: "We have arrested three of the four suspects and have issued an arrest warrant for the other one who is still on the loose.

"The men say they are sorry and that they wouldn't have done this if they weren't drunk."

The father and son required stitches for head injuries, while the mother remains in hospital with serious head and eye injuries, Mr Chaiyakorn said.

The Foreign and Commonwealth Office (FCO) said it had no information on their condition.

An FCO spokeswoman said: "Our staff have been in contact with the family to offer assistance and will remain in contact with the local authorities."

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 whom 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."

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.