The fine of 500 baht/day once notice is given is probably spelled out in the condo rules.
The correct course of action would have been for the condo owner to lobby other condo owners to modify the rules. That's what happened in our building where it was evident that the problem was out-of-control owners of dogs, but not other animals. For a time, all animals were banned, but existing pets were "grandfathered".
After owner input, the rules were changed so that pets that remain in the condo and are only taken out of the unit in an appropriate carrier are permitted. And rules are specific as to how many cats, specifically, an owner can have based on the size of the unit. It's enforced, too.