Beware!
If you buy at TOPS and see a discount on a product, you will get this only with the membership (aka registered phone number). Otherwise regular price.
Saves me a significant amount over the year.
At BigC I sometime save some xxx Baht on points build up. Have no clue
Discounts apply with and without membership.
Makro and Lotus's more or less worthless.
At Makro you get some cheapish stuff after a five digit amount build up (might be 20k or 30k).
Lotus very little purchase.
Never bothered about 7/11 although now proud owner of a TrueMoney wallet (quite handy for small purchases at many shops/services).