For the first time I have used the 90 day reporting in Bangkok  via EMS post 

filled in the required TM 47  plus copies of my passport TM 6 and a copy of the Non O retirement visa plus the self addressed envelope 

sent 15 days before due date to the Immigration in Chaengwattana complex

checked online that the letter had been received day after i posted

one week later i received back the completed receipt of notification plus new reporting date in March  and blank TM 47 

will be using again in March very happy with the service provided

Yes, the EMS 90 day reporting has always been a better option than visiting Chaengwattana Immigration office to do it in person. However doing it online is even better if you are able do it without problems, I have been fortunate to to utilize it without issues. 

I assume that the post office serving Chaengwattana Immigration actually succeed in delivering an EMS 90-day report on the very same day as they receive the relevant container from the local sorting office - in stark contrast to the Maptaput Post Office who, for inexplicable reasons, hung on to my last EMS report for 3 whole days before finally delivering it to Rayong Immigration!