A former police officer was arrested on Friday for the alleged contract murder of a petrol station owner and wounding his wife in Sa Kaew's Muang district last month.
The 62-year-old suspect, Pansak Mongkolsin, was arrested along with his wife Thanaporn Sukkhojai, 50, at a house in Rayong's Pluak Daeng district.
The couple was interrogated at the Crime Suppression Division headquarters.
Pansak is accused of shooting dead gas station owner Pracha Worathat, 52, and seriously wounding Pracha's wife Preeda Worathat, 50, on September 30.
In 1994, Pansak, then a police lieutenant colonel under the command of Central Investigation Bureau former boss Pol Lt-Gen Chalor Kerdthes, was arrested for murdering Darawadee Srithanakhan, the wife of gem trader Santi Srithanakhan, and her son Seri.
The double murders were linked to a Saudi jewel theft case that Chalor was assigned to investigate.
Santi allegedly purchased some of the jewels that had been stolen from the palace of Saudi Prince Faisal in 1989.
Chalor was given a life sentence and Pansak was sentenced to 40 years imprisonment for the double murders. Pansak was released in 2012, while Chalor was released on parole in 2013.