I currently hold a retirement visa I have been to the immigration office for my 90 day report (tm47) and realized that I was one week late I was fined on the spot is this a new rule.

This is not a new rule but has been enforced more strictly now the fine is 200baht per day up to a maximum of 5,000 baht so my advise is put the 90 day report date on your calendar and possibly report two days before the due date.