Why can't I apply directly for a marriage visa after my marriage visa expired?

Your visa and or extension is finished you need to start over so 400K in the bank and yes they may do a home visit

You could reduce the steps by just getting a 90 day Non-O visa based on being married to a Thai before leaving home and entering Thailand on that. Then you would just need to apply for the 12 month extension of stay (which is not a visa) by meeting the criteria for that before the 90 day visa expires

Don't know if this helps but last year I applied on line for my NoneO visa based on marriage.

It didn't come in time for my flight so I entered on visa exempt, went to my local immigration and extended for 1 month.

Then they said when my visa comes through I can extend for 1 year if I have funds in the bank.

In the mean time me and kids went to Vietnam for a week.

When I came back I activated my NoneO visa for another 3 month. Then extended for 1 year.

If regular people can remember my last year I went for my mouth extention at chainart immigration and they give me a year 😄 I was held up at immigration for ages on my way to Vietnam 😄 I got it sorted

What you’re referring to as a “marriage visa” is actually a year long extension of stay. You can only get that for the same reason you got the Non O. You can’t get a year long extension off a tourist visa or exempt entry so you have to switch to a Non O and then apply for an extension.

As you are applying for a Non O based on being married to a Thai national then they are asking for two witnesses.

As to making sense. You’re looking in the wrong place. TiT.