Quick note - Recently came back to Thailand and thought I had to do the 90 day report in person, but I was able to do it online (~ 7 days before due) successfully. So perhaps might be a good idea to attempt the online reporting first, before paying a trip to the local immigration office. The online reporting is also more streamlined now.
TLDR : Answer Summary
The poster recently returned to Thailand and discovered that they could complete the 90-day immigration reporting online, approximately seven days before the due date. They found the online process to be streamlined and suggested that others try this method before going to the local immigration office.