Do I need a police report for a non-immigrant O visa application in Chiang Mai?

get the visa as close to the time you're comin' here as you can

The visa has a validity of 6 months from the date it's issued and you don't want to get it too early and burn down the validity NOT being here.

-When you arrive you be stamped in for 60 days

-when that runs out go to the border, stamp out&back in to get another 60 days

-when that runs out go to the border, stamp out&back in to get another 60 days

-Just prior to the "enter before" date on the VISA itself, go to the border, stamp out&back in getting a final 60 days (taking you to just about 240 days)

-extend that last entry by 30 days for 1900baht at the immigration office taking you to about 270 days or 9 months.

correct (y) you can come in, max out the time you can get from the 6 month METV (which is about 9 months if you do it correctly) then a month before your last entry stamp runs out you go to the immigration office in Chiang Mai and apply to switch from a tourist visa to a 90 day Non-O visa based on being over 50 and by meeting the requirements. It will go under consideration for 21 days then you go back and get the Non-O visa and the 90 day stamp inked into your passport.

THEN when you have a month left on that stamp you go back to the immigration office and apply for a yearly extension of stay (and buy a re-entry permit too if you need one.