I just returned from the Ayutthaya immigration office. Basically the officer told me that even if I meet all requirements for for non-immigrant O extension it would be too difficult to switch in Thailand from my current Non-imm B extension to Non-imm O. The reasoning was somewhat unclear to me but I was told I must go out of the country anyway. Apply for single-entry Non-imm O visa and then do extension.... I just hate the visa runs and dealing with embassy so I wanted to avoid it, but seems like I have no choice. Anyway thanks guys.