I can recommend you change passport first and pay money 8500 baht for agency and enter to Thailand from Suvarnabhumi.Because u stayed very very long time In Thailand in One time.
this is good point but your visa extension every 3 months or 1 time 1 year ED?which one?There are many type of ED?What kind of do you have?And are u sure u are going to lessons?And another question this will be your last extension or not?(i mean last 3months)