@Yaoyu **********
Two main factors in choosing one over the other. 1. Where your money is (or where you want to keep it) , 2. Medical Insurance.
With a Non OA you use local funds (not in a Thai bank - although they could be). Some donโt want to move 800k to a Thai bank where they will gain little to no interest. They keep the money and can use to invest in higher earnings. The visa is valid for one year, but with the right timing can be used for nearly two years. Each entry gives you 365 days, as long as your insurance covers that length.
The downside is the need for insurance. For those approaching or over 70 that can be very expensive or even unobtainable depending on medical history.
With a Non O visa you get 90 days on entry, no insurance required, but within 30 days you need to have opened a Thai bank account and move 800k into it. 30 days prior to your stamp expiring (some offices allow 45 days) you apply for the year extension and re-entry permit if needed.
Once you have a visa itโs irrelevant what flight day you put on the application. You can travel on any date within the validity of the visa. Obviously with a Non OA the clock starts ticking as soon as itโs issued so to get the nearly 2 years out of it you want to travel just after itโs issued. With a Non O visa itโs valid for 90 days so even if you enter 89 days after itโs issued youโll be given a stamp for 90 days.