Can I re-enter Thailand 12 days before my current visa expires to activate a new SETV?

I never heard of a normal triple 60 day borderjojo. But always nice to hear new definitions of a visa.

Maybe just do the normal tripple 60 plus borderjojo and immi-extension so he will be good for one year easy just swap points of entry or immi each time

The minute you exit thailand your current stamp is canceled.

Okay, you're gonna fly in on a single entry tourist visa and get stamped in for 60 days.

Then you're going to apply for a 30 day extension at the immigration office for 1900 baht. They will add the 30 day extension onto your admitted until stamp.

Then you're going to go to a thai consulate and BUY a single entry tourist visa and when you enter thailand you'll be stamped in for 60 days.

Going early won't affect the 60 days you get when you come back with new tourist visa.