Ploen played quarterback for the Winnipeg from 1957 to 1967. He also filled in at halfback and safety. Ploen led his team to six Grey Cup appearances (1957, 1958, 1959, 1961, 1962, 1965), including four victories: 1958, 1959, 1961, 1962 and two losses: 1957, 1965. In the 49th Grey Cup game (1961), he scored one of the most memorable touchdowns in professional football history, eluding numerous defenders on an eighteen-yard run into the endzone during overtime to win it (see video below). He was voted the 1961 Grey Cup Most Valuable Player, was selected as a divisional All-Star three times.