Before reading below realize that:
I do not work at a hotel or in the hospitality industry this is just what I have heard/seen.
From my understanding as long as you aren't getting ash/butts all over the place and don't have 10 people smoking at once so the whole hallway reeks most hotels usually don't really care. If other guests complain or they have to clean up after you that's when you get in trouble/charged money for smoking.