Can a salary deduction policy for tardiness be legally implemented?

I am a global HR manager in Korea and we have a subsidiary in India. They are often late, so I am thinking of implementing a late penalty policy. If an employee is late more than three times a month, their salary would be deducted proportional to the time missed. Is it legal to do this if the policy is included in the employment contract? Also, can we put this as a separate document called “consent for deduction” instead of rewriting the contract?