Was just there last week. Surprisingly they had a list, in English, of the required documents.
- Completed "Application Form for Residence Certificate In Thailand" (no number on the form).
- Passport, copies of first page, visa pages, TM6 departure card.
- Copy of 1 of the following:
Rental Contract
House Registration
Letter from House Master
Not sure how much it is as I just went there to get the form and find out what is needed. I think it is 500 baht.