A secret sect of kung fu assassins could have silenced actor David Carradine as he delved into their shadowy activities, according to his family’s lawyer.

In a twist that could be straight out of one the “Kill Bill” star’s movies, attorney Mark Geragos suggested that Carradine may have been killed as he tried to uncover groups working in the martial-arts underworld.

The lawyer said the actor’s family refuses to believe he died in a sadomasochistic sex stunt gone wrong — despite his being found naked with a rope tied around his neck, wrists and genitals.

Loved ones have urged the FBI to travel to Thailand and pick up the pieces of the police investigation there.

“They’ve done it because of the conflicting reports and the nature of those reports that have given the family great pause,” Geragos said.

The secret societies of martial artists should be the first place they start looking for answers, said the prominent Hollywood lawyer, who has represented Michael Jackson, actress Winona Ryder, wife killer Scott Peterson and singer Chris Brown.

The bizarre claim was made on “Larry King Live” on CNN Friday after a panel member said, “David was very interested in investigating and disclosing secret societies.”

“Absolutely,” said Geragos.

“What that means is connected to martial arts and his interest in martial arts,” he continued. “And so there is a suspicion that if there was some foul play, that that may be the first area where they should look.”

Secret societies in kung fu date back centuries and were originally formed as humanitarian groups, fighting on the side of the people against corrupt Chinese dynasties. But in the last 200 years, many started to turn to criminal activities.

The suggestion they killed Carradine echoes conspiracy theories that Bruce Lee — who, ironically, competed with Carradine for the lead role in the 1970s TV series “Kung Fu” — was killed in 1973 by the Triads, a Chinese secret society.

Authorities said Lee, 32, died of brain swelling triggered by a reaction to medication.

Carradine, who was found dead in a Bangkok hotel last week, had been fascinated with martial arts since he first began studying the discipline upon landing the “Kung Fu” role.

“It’s a way of life,” the actor once said in an interview.

He had dusted off his martial arts moves 30 years later for the title role in Quentin Tarantino’s “Kill Bill” movies.

His ex-wife, Marina Anderson, told The Post yesterday, “If he was involved in secret societies, it was a secret that even I didn’t know about.

“But he did have some big secrets.”

Carradine was found dead in the closet of a Bangkok hotel last week.

Thai authorities think he might have died while pleasuring himself in an act of autoerotic asphyxiation — a practice which involves temporarily cutting off the brain’s supply of oxygen to create a sexual turn-on.

He had been accused of being a fan of “potentially deadly” kinky sex acts in divorce papers Anderson filed against him in 2003.

Carradine’s family has lined up famed forensic expert Dr. Michael Baden — head pathologist for the New York State Police — to carry out his own examination of the actor’s body.

Additional reporting by James Fanelli

adam.nichols@nypost.com