Info only. I have an O-A visa issued in Australia valid until Jan 16, 2020 (issued Jan 17, 2019). Arrived back in Chiang Mai from KL today 13 Jan after 3 day visit. Hoping for another 12 month stamp. IO asked to see Health Insurance, I have the appropriate insurance until Dec 15 2020 and showed him certificate.
I told IO I didn't think I needed insurance as my visa was issued before Oct 31, 2019.
He then stamped my passport until Jan 11, 2021. Very happy with the outcome.
TLDR : Answer Summary
The user successfully renewed their O-A visa upon returning to Chiang Mai, despite initial inquiries from immigration about their health insurance. They were able to provide proof of valid insurance, leading to a new stamp extending their visa validity.