"Every Friday, Saturday and Sunday from now onwards, enjoy 5 Times Membership Rewards points on your spend at Cold Storage.
Click here for American Express Selects offers^ and outlet listing."
If you click "here", it will bring you to:
http://offers.amexnetwork.com/sg/xo-weekends which does not list CS as one of the 5x merchants.
Anyway, tomorrow, 4th Jan is a Friday. Make a charge at CS and once the charge is posted online the next day on 5th Jan, Saturday, you will know if it is still a 5x weekend merchant.