I have no doubt about that.
From the Wiki piece you linked to...
“Ray committed a variety of crimes prior to the murder of King. Ray’s first conviction for criminal activity, a burglary in California, came in 1949.
In 1952, he served two years for the armed robbery of a taxi driver in Illinois.
In 1955, Ray was convicted of mail fraud after stealing money orders in Hannibal, Missouri, then forging them to take a trip to Florida. He served four years in Leavenworth.
In 1959, Ray was caught stealing $120 in an armed robbery of a St. Louis Kroger store.[9] Ray was sentenced to twenty years in prison for repeated offenses.
He escaped from the Missouri State Penitentiary in 1967 by hiding in a truck transporting bread from the prison bakery.[10]”