@Brad *******
, I think you're mixing up entering on a valid O-A VISA and entering on a year extension from an O-A visa
SO few of people are able to "re-enter" thailand that I believe it's a moot point, BUT the way it used to work IS
When you enter on a valid O-A visa you get stamped in for as long as your insurance is valid for (up to a year) and if you leave/come back while that visa is still valid you will only get stamped in for what ever the validity of your insurance is (up to a year) so if your policy runs out in 6 months that's all you get stamped in for even though that visa allows you a year entry stamp.
Now with a yearly extension of stay from an O-A visa <- from the immigration office, you get stamped in for as long as the insurance is valid for (up to a year) AND if you exited re-entered (by holding a re-entry permit) you would still get stamped in for the same expiration date. '