Cambodian authorities have arrested Panya Yingdung, 39, who was wanted for questioning in the murders of his former girl friend and a companion last month in Chon Buri province.
Paweena Namuangrak, 20, and Anantachai Jaritram, 21, were gunned down on July 29 in a parking lot in the eastern province.
Mr Panya, who has been named by other men arrested in the murder case, was reportedly arrested by Cambodian police in eastern Prey Veng province while trying to travel to Vietnam.
Thai police now are expected to seek his extradition. Officers plan to hold a press conference to discuss the case at the Royal Thai Police headquarters on Thursday.
Mr Panya, also known as Sia Uan Bangla, ran a nightclub in Phuket province and was suspected of killing the young couple at a parking lot on Khao Chee Chan (Buddha Mountain) in Sattahip district of Chon Buri on July 29.
Five suspects are already under arrest in the murder case. Police have said they believe that Mr Panya was seeking revenge on Ms Paweena, who had worked at his Phuket club.
National police chief Chakthip Chaijinda confirmed the arrest to Thai police reporters late Wednesday night.