What should I expect after submitting my 90-day report online in Thailand?

You will receive a couple of emails when you submit 90 days online.

The first one is when you submit application. It'd include the application PDF, and

Subject: [TM.47] (PASSPORT NO : XXX0) FORM FOR ALIEN TO NOTIFY OF STAYING LONGER THAN 90 DAYS RECEIVED

The second one is when your 90 days report gets result. It'd include 90 days report receipt PDF (RECEIPT OF NOTIFICATION) if approved

Subject: [TM.47] (PASSPORT NO : XXX0) FORM FOR ALIEN TO NOTIFY OF STAYING LONGER THAN 90 DAYS HAS BEEN APPROVED

or

Subject: [TM.47] (PASSPORT NO : XXX0) FORM FOR ALIEN TO NOTIFY OF STAYING LONGER THAN 90 DAYS HAS BEEN REJECTED

You also can check the status of your report and PDFs on the online system.