Previously, the company had implemented a new policy on the employee salary. They divided our salary into 60%, 10% and 30%.

1. 60% is the fixed amount that will be paid each month.

2. 10% is based on our attendance.

3. 30% is based on our performance of that month.

Now, they required us to re-sign the employment letter that included this policy. Is this illegal and can I refuse to re-sign the employment letter?