just for ur info singapore got no age limit. Its just that some shops have the 18 rule so ur parents wont come to thier shop and argue with them for doing ur tattoo without thier consent. I know this cause I know alot of artists... And It came out on news that they might be considering to add age limit.
Most shops put the sign just for show la. But there are a few shops that are rather strict. I think body decor's quite strict. They didn't allow my cousin to pierce her tongue when she was 15.