Yes you can apply for a 90 days Non O visa based on being married to a Thai from your country. You can probably apply for the initial visa by proving income minimum 40K baht a month but you’ll need to prove 400K baht in a Thai bank account two months prior to your application for extension of stay in Thailand.
You can apply from home just with income or funds as Lester explains and also in Thailand if your embassy in Bangkok offers to give you a affidavit letter regarding income.
Requirement varies slightly between immigrations. Best to get handed over the requirements in CM before you apply. Reports of only randomly home visits for the retirement extension.
I just use bank to bank transfer myself within maximum a couple of days. Some use Wise as I understand goes quite instantly if that’s an option for you. Not particular expensive.
No you can’t apply for a Non O visa in Savannakhet without proving funds any more and the multiple option is not available, only 90 days Non O based on marriage with single entry which you can apply for a one year extension of at your local immigration in Thailand and apply for multiple re-entry permit to get stamped back within the validity of your stay. The requirement are anyway 400K baht in a Thai bank or 40K baht a month within Thailand. Some immigrations accept affidavit letter regarding income.
You can apply for the initial 90 days Non O visa before you come by proving income min 40K baht a month