Nine Thai couples locked lips Tuesday in hope of setting a new record for the world's longest kiss, but the attempt proved too much for two septuagenarians who dropped out after just one hour.

The participants, who must kiss for more than 50 hours, 25 minutes and one second to enter the Guinness World Records, were forbidden from sitting down and could only go to the bathroom after the first six hours.

"They have to continue kissing while they go to the toilet and can only drink water or milk through straws," said an event spokeswoman.

"They couldn't do this unless they love each other. The smell of their breath would probably be quite something."

The current holders are a male couple who returned to try to beat their own record set last year.

"I'm 100% confident that a couple will break the record," said Somporn Naksuetrong, the vice president of Ripley's Believe It or Not! in the resort city of Pattaya which hosted the event.

The oldest entrants to sign up in hope of winning the prize of 100,000 baht ($3,300) cash and two diamond rings were a 74-year-old man and a 72-year-old woman celebrating their 50th wedding anniversary.

"They quit after about one hour. It was the first time we had old people joining," Somporn said