If you have been living in a Thailand then it sounds like you are on a 1 year extension of stay. Did you apply for your current extension of stay based on retirement or marriage? If you did it by marriage then I think you don’t need to have insurance.
Many of us arrived on O-A visas before the health insurance requirement. In any case, you can meet the O-A financial requirements using money in banks outside Thailand. That feature is appealing to many people.
You should consider coming on a tourist visa and transitioning to a non-O and then a one year extension. The advantages of an O-A are not what they used to be.
And when do you have to do it? Go as early as possible so you have time to fix anything that goes wrong. If in doubt bring more documents than you need. Take notes for next time.
Ben Sevilla You have an extension of stay, not a visa. Do you have your original visa in your passport? If it is a new passport then try looking at the first page. Most visa advice is going to depend on this information.