I heard that people are required to report their residence address immediately upon arrival now. The arrival card alone is insufficient. For people staying in hotels, this is no big deal because the hotel reports it. But for people who own or rent their own room, they must register in person within 24 hours of arrival. A friend of mine got fined 1600 baht for not doing this. I arrived in October and reported on a 90 day last month and had no problem, so apparently this is a new rule ? I heard the fine can be as much as 4000 baht.