Will I be allowed to extend my stay in Thailand for another 30 days after my initial 6 months?

that is the magic question and not a single person on this group or in the world can give you an accurate answer. It comes down to your previous entry history to thailand, and the mood of the person at passport control you get when you're stamping into the country on that day at that counter.

There is no way to say YES you'll get right in, or they'll question you but let you in OR nope you'll be denied entry.

Have the 3 proof ofs, proof of funds (20K baht or the equivalent in CASH) proof of onward travel (within the days you'll be stamped in for) and proof of lodging and hope for the best..