my point is that it is written that the letter should be no older that 7 days, however, it appears to be the case that if you try and give a bank letter that is anyway near 7 days old, immigration don't want to accept it.
In Bangkok, 90 day reporting can be done in person, by mail or internet, I assume in person is available but are either of the other 2 option available.
Also for 90 day and yearly exemption renewal the is an online appointment booking system usually available, again are either of these services offered?