It's hit or miss depending on how many people are extending that type of visa that day. Last week, I extended ED visa in Chiang Mai, arrived 6:45am and I was #44, done by 1:30pm. #7 sitting next to me had arrived at 4:30am.
Or re-start a new ED visa while I am still in the US at a Thai consulate here? And enter on a new ED visa? Is that possible without cancelling my previous extension?
So, should I just enter on a visa exemption stamp? Will it be a problem getting through immigration with my non-cancelled ED visa? I will have documentation from the hospital saying that I couldn't fly until after the date my re-entry permit/ED extension expires.