Just to let everyone know: I went to Korat Immigration yesterday for my yearly extension on my non-immigrant O visa. I had all the papers( or so I thought) and I have to say the reception was fantastic. At a certain moment the officer discovered I had included a copy of my rental contract of last year, and she and her superior went out of their way to help me. They contacted my landlady and asked her to send over a photo of this year's contract, printed it out in the office and added it to the file! Saved me a trip to Phimai and back.
One thing though, she said that next year I'd have to show the original owner's housebook as well. We'll have to see what we can do about that.