technically no problem, but wont get rm2 discount. 

that is if the barista dont refuse to use ur tumbler in the 1st place.

Yups, i thought so too. For sustainability purposes. Anyways, i went to a starbucks that will not accept my own tumbler. So, oh well. But some of them do accept my tumbler though. So it depends on the starbucks chain itself.
Edit: btw, some starbucks tumbler are having a 30% sales currently till the end of march 2017.

environmental concern yes, but they are still business company.

it's one of the way to make profit.

Yups, although they accept my own tumbler, im not entitled to the rm2 discount. What to do lorh..

Not too sure about the expiry date. You can check ur credit balance from starbucks malaysia apps though.

Yes, the card will be expired after 3 years from last transaction

You can plan to make transaction during your birthday month (registered month) so that a complimentary cake will be for you then

You mean during your birthday month, every time i use starbuck card to purchase coffee at starbuck, i will get a complimentary cake?

who is that? got such guy?

to have 12 card which get a free cake also consider too much already

Means just walk in buy a coffee (even with cash) and show ic, then can get the free cake?

Went to Starbucks just now, and the barista showed me the card. I asked him what's so special about it, he said that it's very limited. From the city where i come from, he says that there are only 10 of this card available. So yeah, really limited. But what's so special about it? I really dun know. I asked him, he was also not sure. 😁