"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