What documents do I need for my first 90-day reporting at MTT in Thailand?

You ONLY need your copy of the TM30 that was filed for you showing where you stay and a filled out TM47 to file a 90 day report at MTT

EDIT; you WILL need to have the stuff you're supposed to have in your passport IN it when you file; the TM6 departure card, the TM30 receipt, and the little paper they gave you telling you when your first 90 day report was due