Walker and winger Alex Johnston then added more tries as the Rabbitohs ran rampant, racing to a 22-0 lead.
Gold Coast winger Anthony Don managed a brace of his own to reduce the margin to 10 at the break before Walker snared his first NRL hat-trick three minutes into the second-half.
Titans' co-captain Greg Bird will have a nervous wait ahead of the NSW State of Origin team being named after he was placed on report in the 60th minute for a dangerous tackle on Bryson Goodwin.
Walker, who had been denied a fourth try by the video referee, completed his great day with 13 minutes to go before Johnston's second capped the victory.
Luke Burgess was placed on report late in the game for a shoulder charge which left Titans' forward Ashley Harrison groggy in an almost solitary bad moment for the Rabbitohs.
The win is the Rabbitohs' fifth in a row against the Titans and keeps them in the top eight with five wins and four losses this season.
The Titans, who travel to rivals Brisbane next weekend, have a six win and three loss record.
Meanwhile, the NRL are reportedly investigating allegations their head of football, Todd Greenberg, had knowledge of front-rower Ryan Tandy's gambling on rugby league games while he was Bulldogs chief executive but turned a blind eye to it.
Fairfax Media reported the claims Greenberg was given evidence of Tandy betting on league games but took no action have prompted NRL chief executive Dave Smith to request an investigation.
"These are allegations which go back three years," an NRL official said. "However, the NRL takes such issues seriously and is making inquiries into the matter."
The death of Tandy, 32, last month from a drug overdose has shifted focus onto his troubled former first-grader's life and the spot-fixing scandal over which he was convicted and given a life ban from the code.
The fresh claims centre around Greenberg who was CEO at the Bulldogs when Tandy was involved in the game against North Queensland in Townsville and when the prop was subsequently sacked by the club.
