Morin tendered his resignation after the PSX board of directors issued a show-cause notice asking him to explain his simultaneous working with a Canadian wealth management company, the Express Tribune reported.
Earlier, the board had issued him two letters and was not satisfied with his explanations, the daily said.
According to Dawn newspaper, an emergency meeting of the PSX board of directors was held on Tuesday during which Morin submitted his resignation.
"We would like to inform you that Richard Morin has tendered his resignation from the position of CEO of PSX Limited, which was accepted by the board of directors with immediate effect," Company Secretary Muhammad Rafique Umer said in a notification.
Morin joined the PSX as the first non-Pakistani CEO in January 2018 following its demutualisation and corporatisation about a year before.
According to the board, Morin had simultaneously been serving in Archer Wealth Management Inc Canada as its Chairman and Chief Compliance Officer.
"PSX rules and regulations suggest that if a high official is found to be in conflict of interest and does not meet the 'fit and proper' criteria for the high position, then he should be removed with immediate effect," a PSX director said.
Morin completed his B.Sc in Economics from the University of Montreal and an MBA from McGill University. He co-founded Montreal-based investment manager Landry Morin Inc. He has also headed the Stock Exchange of Mauritius. He had also been vice-president of National Bank Securities.
( With inputs from IANS )