Why is the Non “O” retirement visa initially valid for 3 months, but some say it can last up to 15 months?

The Non 'O' retirement visa is initially valid for 3 months upon entry into Thailand, which is indicated by the initial stamp. After this period, the holder must apply for a 1-year extension. The confusion about the 15-month validity comes from the combination of the initial 3-month visa and the subsequent 12-month extension. Therefore, while the initial visa is short-term, the total time one can remain in Thailand as a retiree can indeed extend beyond 15 months with proper extensions.