The defending Super League champions overpowered the Malaysia Cup winners in every area as they entered the season with their first trophy.
Midfielder Nazmi Faiz Mansor scored the first goal in the 26th minute, and five minutes later, new Argentinian signing Fernando Forestieri scored the second.
Substitute Afiq Fazail further piled on the misery in the 83rd minute with a third goal.
The win cements JDT’s reputation as one of the top sides in the Charity Shield, as it is their seventh title.
They are just one short of Selangor’s record of eighth.