Here is my list for supporting a Thai child, but if ignore birth the certificate, its very similar, this reflects my circumstances and where ive been asked for additional ive added them in each year
Yes it should be possible, but check with your office as your probably aware each office can interpret visa extensions differently. I've swapped 3 times for different reasons.
yes, a friend of mine is processing an ext based on being over 50. He told me they have asked for documents more online with a Thai wife visa, like photos outside the house, crazy, its these exception that make the process so unpredictable