My 90-day reporting is due Oct. 10 and my retirement visa expires Oct. 25.

My hope is to appear in Chaeng Wattana and handle both procedures on the same day. How many days prior to my annual renewal will Immigration accept my application?

And for future reference: how many days prior to my 90-day deadline will Immigration accept the form?

Extensions = usually 30 days.

90 day reporting could be done 15 days early to 7 days after.

Correct. You can do both transactions in one visit any time between now and 16 October.

You can apply for extensions up to 45 days early at Chiang Watanna so no problem doing both on the save visit.