@Aki ***********
GO file a 90 day report in person NOW and it will totally be up to the discretion of the officer on whether you will get a 2000baht failure to file on time fine or not.
You can't use the online web-site or mobile applications if you're late, YOU have to go in person (meaning you can't send someone for you).
Just go get it out of the way now while the immigration offices aren't busy