Michael Taylor, 50, was arrested in Phuket in 2005 for allegedly stabbing Jantra Weangta to death. He fled Thailand midway through his trial in 2006 and was spotted in the Philippines in November last year, the Hull Daily Mail reported.
It was reported that he had also travelled to England during his time on the lam but this could not be confirmed.
Mr Taylor, an offshore worker known as "Mick the Pom", was arrested in the Philippines last month after his visa ran out, the newspaper said.
But Chiengsean Panhya, Phuket's chief public prosecutor, says he cannot pursue the extradition without a formal request from the police.
"I don't have the authority to pursue it unless the police ask me to," he told the Phuket Gazette. "Our office is not even permitted to ask the police to file such a request."
Once police do file a request, it must be forwarded to the Office of the Attorney General in Bangkok, and it would be up to officials there to pursue Mr Taylor, said the Phuket prosecutor.
The body of Jantra, 27, was discovered in the rented bungalow she and Mr Taylor shared near Chalong Beach.
Mr Taylor denied killing his girlfriend, claiming he had been having sex on a beach with a ladyboy at the time of the attack.
Police recovered a large Bowie knife and a pair of bloodstained pants, and prosecutors had lined up 13 witnesses, including a DNA expert, to testify against Mr Taylor.
Despite the seriousness of the accusation, Mr Taylor had been granted bail on the strength of a land title deed valued at 400,000 baht.
He fled Phuket in 2006, midway through his trial, which had been delayed on several occasions.
According to the Hull Daily Mail, Thai authorities were informed in November that the owners of a bar in Pundakit, about 160 kilometres from Manila, claimed they had heard him bragging about the killing.
The officer in charge of the case, Lieutenant Col Danprai Kaewwehol of the Phuket Provincial Police, told reporters earlier that he had been "too busy" to follow up on Mr Taylor's case.
However, he has insisted that he wants Mr Taylor extradited to Thailand and said he planned to hold talks with prosecutors.