I was wrong in I thinking the limit was THB 1,000. But don't forget that the card is now accepted in many Food Courts for payment.
Seeing as one needs ID to apply for a card, it would be on record somewhere if someone went to all the trouble apply for multiple cards.
Also if you look at the Rabbit Terms and Conditions, (they no longer appear to be available on the internet), they are quite Big Brotheresque in how applicants agree to be tracked. I did post them on this site once, but they were removed by a Mod. for whatever reason.