Do you have a 3-month ED / extension? So with a private school? then your visa gets automatically canceled once you leave the country without a re-entry permit. very easy. no cost. nothing else to do besides leaving. You can then immediately apply for the DTV once you passed immigration. i did the exact same in july 2024.
if you have a multi entry ED (with a university for example) then you might want to cancel it inside thailand first.
you can extend your 180 days by another 180 days. check with your local immigration office what there specific requirements are… but you will need all documents from your application again with a fresh date and ongoing activity. some offices also require extensive residency proof. check with the IO
sorry, i cannot comment on that. but i would guess if it is possible somehow then it would be incredibly complicated with all the paperwork. if you know the right people then everything is probably possible. just a matter of money ;)