A acquaintance of me get denied entry yesterday comming back from Ireland after being there 3 weeks and before he stayed less then 90 days in Thailand on a 60 days exempt plus extension.
Maximizing your stay with back to back entries will eventually fail. Recently more people got denied entry even after just one stay.
Not the foreigner but their landlord, host or hotel need to report any foreigner staying at their property. For those foreigners who need the TM30 for doing business at the immigration its advised to remind your landlord/host/hotel about it. Only in case of owner your own property you need to report yourself.
Comming back from abroad to the same adress doesnt automaticly mean the previous tm30 is still valid. It depends on your local immigration. Some still ask for a update. Some you don't need that.