I wanted to reduce my CIMB Home Loan so I called CIMB call centre on how to do it. It was really surprising how easy it is.
Just login to your CIMB Clicks account. You will see your home loan at the dashboard.
1) As usual, when you want to pay for your Home Loan, you click:
Pay & Transfer -> Pay Loans & Cards.

2) Then select, your home loan account. At bottom on payment option, you choose Reduce Loan Principal.

3) After the transfer, go immediately to your CIMB Clicks dashboard, the home loan principal will be reduced immediately based on your transfer amount.