Company can reduce salary structure to lower as per compliance - if employee wants fewer hours of duty?

Dear sir, If an employee has joined the company for 12 hours duty and getting 15,000/- salary - after that employee wants to do 8 horse duty and get the salary of 12,000/-, can the company reduce his salary structure to lower as per compliance.

Dear Vikram,
Any contract of employment providing for 12 hours-a-day duty is void as it is violative of the statutory norm of working hours.
Therefore, reduction of the already agreed salary in proportion to the reduced working hours even with the unequivocal consent of the employee is still questionable. However, if it does not fall below the statutory rates of minimum wages,if any fixed for that employment, such arrangement would be so far so good.

There cannot be a regular 12 hour duty every working day, it is against law. Normal duty hours are 8 per day. So there cannot be reduction in pay by Rs.3000/- for conforming to the law. Now in most places the minimum wages would be more that Rs. 12,000 for any skilled type of job. Once employee starts regularly getting Rs 15,000 pm it cannot be suddenly reduced to Rs. 12,000/-., it would be an illegal change in the eyes of law. If the matter gets reported to the Labour Department, the company would be really hard put to defend the matter. Such unilateral action should be protested and challenged.