It sounds as if the divorce is amicable for the moment and the wife is pushing hard for that. Were you married in Thailand or elsewhere? If elsewhere you need to have the marriage registered in Thailand at the Amphur and which should also indicate you are the father of a half-Thai child. This could be the reason your name is not "coming up". I assume you have a legal document attested by a lawyer setting out the terms of the pending divorce. Why not visit immigration, with wife and child and together detail to the IO exactly your predicament and ask best means for you to change your visa/extension reason, and for wife to move on.
I called due to an emergency requiring my Thai wife needing to be placed into a hospital for final stage Altzheimers/Dementia which has left me a little short of income. But no! we telephoned and spoke Thai. She was very clear about seasoned for two months prior to extension application as well as only one month after approval. I will NOT be tempting fate, so will allow two weeks to get bank statement (assuming will need to come from Bangkok) and next time round could well be a different individual.