So I went to Jomtien Immigration, yesterday with my documents.
First thing they check your passport for having a current TM 30. In my case, my realtor agent (I rent) provided me the page printout from the on-line TM 30 registration last time i entered country. This form does not have the portion at the bottom that you cut off and attach into your passport. So first thing IO at info counter did was she sent me to the TM 30 counter (counter 10) whereby an IO completed the normal receipt slip and attached it into my passport then sent me back to the information counter. I asked if there was an official list of required docs for a Certificate of Residency, she said "no hab".
Next the IO at the information counter took my 2 separate document packages and combined them into one app package (I was requesting COR for trading in a motorbike at a Honda dealership), noting on the application form "for buy & sell" and discarding much of the information I had brought (sales receipt, Green book) ect.
While I didn't get an opportunity to review the final package, as best as I could tell, What they wanted document wise is the same as what brianthainess posted above for Trat.
One thing I thought somewhat odd was they wanted 3 passport photos? Not sure why but whatever, TIT.
Information desk then sent me to counter 9, where i paid the 300b x 2=600b fee, they accepted the document package, gave me a plastic number tag and told me to return in afternoon at 4:00 pm to pick up.