How do I legally exit Thailand on an ED visa while applying for an OA Visa?

Hello everyone and once again, thank you to the group and Moderators. Very helpful stuff here.

Per my last post, I'm going back to Los Angeles to get my OA + 50 Visa from the L.A. consulate (as suggested) My question is how to get out of here legally with no problems.

I am currently on an ED visa which requires my 90 day report on 17/09 and actually expires on 26/09. My flight to LAX is 15/10.

My thinking is to just do 90 day report on line. Cancel ED visa @ CW on/about 20/19 Border Bounce (land)before my permitted exit date expires (last entered Thailand @ Nong Khai Dec 2018) to get 30 day stamp with an exit pn October 15th to get the OA.

Am I missing anything?

TIA