@Carl **********
, that TM6 is an arrival/departure card, given to you when you arrive, they take the arrival part of it and you have the matching "departure card" piece in your passport.
As I said, when you arrived you or your land lord should have went to the immigration office and filed a TM30 (that's the form that says a foreigner is staying at xxx residence). You file a new TM30 with the immigration office every time you come back into the country (although some offices want you to file a new one every time you come back in to the province, so check with YOUR immigration office.
Another things (totally unrelated) is 90 day reporting. You do that when you have been in thailand 89 days from the date you stamped in.
As I said, you can do a 90 day report 15 days before down until 7 days after your actual due date.
The only time you don't do a 90 day report is if you leave the country before the 90 day due date. Then the count down resets when you stamp back in and your next 90 day report is due 89 days from the date you stamped back into the country.
90 day reporting is free and you do it at the immigration office in your area where you live. Once you do one in person (to get into the 90 day data base) you should able to use the online system for your future 90 day reports