Officially not married so not a spouse. So both of you would need a separate application and qualify on their own.
I don't quite understand your comment on the bank account either... The bank account doesn't need to be in Thailand. Your partner couldn't open a bank in their home country or other country where you are?
Either way, to qualify each applicant has to be able to show a bank account in their name with 500k baht. Supposedly some say there is a way for a "sponsor letter" but haven't seen any reports of it actually being done
TM30 is a report made by the property to immigration where you're staying in Thailand.
Then you need to do a 90 day report to immigration if you've stayed in Thailand without leaving for 90 days. It's basically and update so they know where you are. Very simple
where did you hear this from??? Hahaha not true at this time.
No need to show bank statements every year or upon re-entry (assuming not using an extension because that is unknown and might vary between immigration offices)
Just do a border run. It's easy and you don't have to do any paperwork or anything, just show your DTV letter. When you return you'll get another 180 day stamp.