I got LMG, 200k deductible, to meet OA requirements and most likely will never have any other use for it. Cigna inpatient is my key insurance, but not certified for OA requirements - but that might change later this year. This image shows rates from about July of last year.
A multiple entry OA allows you to enter Thailand an unlimited number of times as long as the original visa is valid, which is one year from the date issued. Each time you enter you get stamped in for one year, which allows you to stay for one year from the date of that entry.
Clarification. Upon completing my extension, the IO reminded me I would still need to do my 90-day reporting, which had an appointment/due date of about 3 weeks after my extension - which was my first extension based on an OA Visa based on being over 50. I now recall that I did that 90-day reporting in person, only because I found it easy to do since I live close to immigration. After that, I completed the next one online without any problems. The timeline or due dates of my 90-day reporting never changed due to getting my extension of stay renewed.
I have successfully completed an online report after an extension of stay, and the timeline I used was based on my prior appointment or due date for 90 day reporting, with no change due to the date of my extension to stay. I have subsequently completed one 90 day report via EMS post, which I mailed 10 days before that due date, which worked fine.