Sorry for posting on this thread, but I was going to ask pretty much the same question. Just to clarify, if my extension (based on marriage) expires on September 26th, then I can extend it at any time as long as it's less than 45 days before September 26th, which is when the extension expires......Is that correct? Thanks :)
Steven Wayne Simpson Yeah I've been thinking of that. I was planning on using half of it to put a down payment on a house......But trying to save up and reach 400k before July-August would be far riskier for me than saving up over 10-12 months...... :)
I think my other best option (apart from switching to a Non-B) could be to get a 60 day temporary family extension when my current extension is due to expire since I haven't used mine yet. That would give me a bit more time to top it back up.......  
Tod, thanks for the message and the info about needing to apply 14 or 21 days before my current extension expires. That's really good to know and I'll contact Chaiyaphum immigration closer to the time about about that.........Do you think the same 14 day (or 21 day) rule would apply if I was to switch to the 60 day temporary family?
Ah, ok. Thanks Tod. I remember before CO-VID there was the 7-day emergency extension which people would use after they cancel their Non-O/Non-B to give them some time before leaving the country.......I guess switching from that to the Non-O extension without leaving the country isn't an option then? :)