your need for multiple entry isnt an issue ...you just buy a single or multiple re entry permit as required either from an immigration office or at suvarnabhumi airport. Much more important is to maintain your yearly visa extensions ...otherwise back to square 1 getting a new visa with all the cost and hassle
my point was that I take out insurance covering any enty and O requirements as a supplement and thai backup to my existing uk cover ...I like to cover all the bases.
I no longer do OA because you are indeed directed towards poor and expensive cover
see Benjamins answer. Essentially a non imm o is for 3 months and then an in thailand extension (yearly in my case as I live here). A re entry pass is obtained on each exit from thailand (I only visit family in uk once a year) so single. A multientry pass allowing 3 reentries is an alternative option. These are also obtained in thailand prior to leaving and return.
I have had both non imm oa and o extension based on retirement ...overall, particularly if you already have 800k in a thai account I found the o retirement extension option both easier to get and overall cheaper due to less certificates and insurances. Particularly as you pass age 65 and insurance premiums rise steeply often.