I think that my today experience will be useful for everybody. I went to Chaeng Watthana this morning ( August 8 ) and around 13.45 I showed my TM47 request. I showed also the email of the immigration office which I received yesterday (August 7) around 17.45, inviting me to go to the Immigration Office asap because my online application was rejected. The officer did not mention anything about the delay, she performed her duty and just informed me that the rejection was due to the fact that it was my first 90 days report after changing passport. Therefore 7 "real days" beyond the expiration are ok ( from 1st to 8th ). Thank you and bye bye. Case closed.