The convicted felon who played Dr. Evil henchman Random Task in the original "Austin Powers" movie is now suspected of murdering his prison cellmate ... TMZ has learned.

Prison officials say Joe Son -- who's already serving life in prison for torturing a woman in 1990 -- is the prime suspect in the murder of a 50-year-old sex offender, who was sharing a cell with Son at Wasco State Prison in central California.

Officials say the victim's body was discovered yesterday. The victim was serving a 2-year-sentence for failing to register as a sex offender.