Some questions:

1. If use maybankard amex for interest free installment plan on a weekend, will get 5% cash back or not?
2. If use maybankard amex for interest free installment plan, will get 5x treatpoints or not?

This is not fine nor acceptable. Please have you opinion and thoughts corrected. Small or big business ... nothing give you the right to break rules for the sake of profits.

It contravenes the T&C between the merchant and the bank. Under the VISA and Mastercard International, merchants are not supposed to penalize customers who uses credit card through additional charges. Customers are not supposed to support retailers who do this but instead to report them to the bank. Consumers who are unaware of this illegal practice by merchants to take note that merchants hide this transaction by "merging" the additional charges into one single price.

Should they are caught with evidence to prove their wrongdoing, VISA/Mastercard + Banks will penalized them so much money that they will cry.
Please consumers .... do not have the mentality that this is right. It breaks the rules and we are helping them.