yep, sounds like your first 90 day report is due about Jan 8, 22 (90 days after entering Thailand.) Keep in mind that you can report up to 15 days before your due date and 7 days after.
I learned something new today because of your response to this question. I'd just like to take a moment to thank you for all of the wisdom you routinely impart on this group. Unlike some of the other more knowledgeable members, who are IMO far too often condescending and even borderline abusive, you never fail to be polite and helpful, regardless how trivial the question may be. I for one, truly appreciate what you bring to this group. Thanks again and have a happy Halloween!!