Encash of Public Holiday

When a company decides to en-cash all the public holidays or incorporate into the hourly basic rate, please advise the following scenarios:
Is employee required to work if the PH falls on his working day since the PH had been encashed?
Employee is required to work on Public Holiday if the company has encash the "one day salary" to the employees

If the PH falls on a non-working day, must the company give off-in-lieu?

If the Public Holiday has been encashed to the employee, there is no longer any off in lieu shall be given.