Many thanks to UbonJoe, Skatewash and LopBuri3 for their replies. Yes, I was aware the passports aren't printed in Thailand and when I got my last passport 9 years ago the requirement was to apply in person, then the passport application + old passport were sent to the US and I went back 2 weeks later and pick it up.
I see now they are promoting the mail in option. I was mistaken earlier because I thought for some reason that I had to mail the application overseas and wait for the new passport to arrive. Now I see that the transaction is with the US Embassy on Wireless Road. It's less than a mile or two away from my residence and even closer to the post office, so sending by registered mail should suffice. I see now they even have an option to pay online in advance for Thailand residents. Great!
Also noted the advice about making copies, photos of passport details including entry stamp and latest visa extension in lieu of passport. Two weeks or so seems like no problem to wait for the new passport to arrive.
My remaining issue is timing. I was told at MTT that the visa extension is only good for the duration of the passport. So if I go in May to make the extension deadline, the new date will only extend to March 2023 instead of early June as now. Also, I think the passport becomes pretty much useless to travel internationally 6 months prior to expiration (not sure about domestic travel), So I'm guessing it would be best to renew a few weeks before I normally go and get the extension and then get the new passport transfer stamped at the same time I get the new non immigrant O extension. Although I wouldn't want to cut the timing too close. Is there any advantage to doing the passport renewal right away and making an extra trip to CW for the transfer stamp or will the canceled old passport invalidate my current visa and if so, how many days do I have from receiving the new passport to report this to immigration. (I may also be planning domestic travel around end of March / Songrkan period which could further complicate the schedule).
Anyone with relevant experience / advice, kindly respond. Thanks very much!