@Bosco ******
if you're speaking about the 1 year multi entry non-o, that visa has a validity of 1 year, and each entry gives 90 days of stay. That means during the validity period of the visa, you are able to enter Thailand with it as many times as you want, but stay no more than 90 days at a time.
Basically it means you have to exit/re-enter Thailand every 3 months.
If you re-enter Thailand juste before the visa expiration date, you will be stamped in for 90 days again, so that means you would be able to "be here" for 15 months. Then when those last 90 days are about to end, you can still apply for a family visit extension from the immigration office inside of Thailand, to get an additional 60 days. That means that visa would allow you to stay in Thailand basically 17 months if you time it right.