I also preferred O-A before and insurance I got my German one which supplied all necessary signed docs for my O-A visa and I will keep that one even it's not mandatory for O visa.
I also know immigration could be a pain in the a ..
Nevertheless , COVID teached me it's not that bad to do all the visa stuff inside the country.
you have to make sure you also have insurance for the "2nd year" of stay stamped in when you bounce shortly before your O-A visa finished.
If you extend O-A visa inside Thailand you will get O-extension and that will be always based on the original O-A visa, means you will also need insurance.
I will now change my O-A visa into O visa ( without insurance requirements )
by leaving the country when my "2nd year" is finished and apply outside for O visa and doing extension inside and now this will be based on an O visa.
I'm planning also to finish the O-A . So I'm leaving for holidays in Germany and I will come back on Non-O visa and then applying for extension based income/affidavit here in Phuket.
read the rules about O-A. All explained there. Every time, during the validity of the O-A visa , you will be stamped in for a full year at every entry. ( Watch your insurance validity!)
Leaving and returning shortly before your visa finish will give you the 2nd year of stay .Voilà . ( 2nd year needs a re-entry permit if you want to travel abroad)