Take some of the so called experts comments with a pinch of salt. There's plenty of visa experts here on Sadbook that don't know what they are talking about.
Seems you don't know what your talking about. Applying for any visa doesn't mean your passport cannot expire before your visa does. I applied and got a Thai visa many years ago and my passport was due to expire before the visa expiration date, so I renewed my passport at the British Embassy in Bangkok, went to immigration armed with my old corner cut passport with my visa in hand. My new passport and immigration transferred my visa from old to new.
I have mates who are married to Thailand ladies who I used to work with and they all told me that to get a non-O based on marriage they only show 400k in their Thai bank account and similar when they go for the extension based on marriage they only have to show 400k in their Thai bank account. They have never had to show a monthly income to get their extension, or so they told me.
I didn't know you had to show a monthly income. I thought all you had to show to get the extension based on marriage to a Thai was a Thai bank account with at least 400k deposited.