How should I handle TM 30 and TM 47 reporting after entering Thailand on an OA visa?

No worries, wherever you are staying will file a TM30, once you get to your home you get your landlord/self to file. The most recent always supercedes the previous. Your first 90 day report will always be in person at your local immigration office, you have 14 days before and up to 7 days after the due date to appear in person. Subsequent filings can be done online if you stay 90 consecutive days. You can file online between 14 and 7 days before the due date. From 6 days before till 7 days after you must go in person.

The owner of the property must report you within 24 hours to immigration. If you stay in a hotel they file a tm30 move to a new location new tm30, etc.

90day reporting is a separate form. They may want a copy of your most recent tm30 to prove you have been registered where you are staying. Be careful if to make sure the 90 report is filled out with the location of your most recent tm30 or the system may flag it.