@Colin *******
an OA visa (that you get in your country before you come here) is an unlimited entry visa that gives you a year entry stamp each time you come in (or as long as your insurance is valid for up to a year)
The visa is valid for a year, so if you get NEW yearly insurance and bounce out/back just before the VISA itself expires you get stamped in for a whole new year (or as long as your insurance is valid for up to a year)
Most people on OA visas get 2 years of stay in thailand out of a visa that is valid for one year by doing that.