Hey Chris, so the income method needs to be over the last 12 months, can't be based on future salary. If you don't have the 400k in an account 60 days (pretty sure it's 60) before applying for a yearly extension, you can't get the extension.
2 options would be either exit Thailand and reenter visa exempt, then apply for a new Non-O based on marriage (90 days), put the 400k in an account and apply for a yearly extension after 60 days,
You're over thinking it. Immigration doesn't care where your visa was issued at. Very common to get a visa in the US for Thailand, go to Bali, go to Vietnam, then go to Thailand.