Can I Get a Non-O Visa for 90 Days in Thailand to Apply for a Marriage Visa?

To get the 90 day Non-O visa at the immigration offices that issue them (because not every one can do it) you need to have so many days left on your current 30 day entry stamp, 60 day tourist visa entry OR the an extension from one of those stamps).

Most offices that can issue the in country Non-Immigrant visas need 15 days or more left on your current stamp, because the application goes under consideration for 14 days before you go back to get the Non-O visa and the new 90 day stamp inked into your passport.

Some offices require 21 days or more left on your stamp because that's how long their under consideration period is

What you have to decide IS

Can you meet the proof of funds (400K baht in a thai bank account in your name for 2 months) before you apply for your 90 day Non-O visa at the immigration office?

If the answer to that is no, then go to the thai consulate in Savannakhet Lao or Ho Chi Minh City Vietnam and get either the 90 day single entry Non-O visa OR the year-long, multi-entry Non-O.

Okay, marriage visa is a term bandied about as a "catch all". In reality there is no such thing.

There are two ways to get long term stay here

Get a 90 day Non-O visa based on marriage to a thai (either at the immigration office inside the country by meeting the proof of funds and submitting the required documents) OR at a thai consulate in another country (which may or may not require proof of funds).

get stamped in for 90 days, when that runs out apply for a year extension at the immigration office by meeting the proof of funds (400K baht in a thai bank account in your name only for 2 months before you apply).

OR

Go to a thai consulate that issues a year-long, multi-entry Non-O visa based on marriage that does not require proof of funds (Savannakhet Lao or Ho Chi Minh City Vietnam) get that visa, get stamped in for 90 days, when that 90 days runs out, go to a border, stamp out of thailand, stamp in&out of another country, then stamp back into thailand for a new 90 day stamp <- you do that for the whole year the visa is good for..

Go to Savannakhet, apply for a non Immigrant O single entry, that will give you 90 days. After 60 days go to your immigration office and apply for a year extension.

What is a "marriage visa"? There is no such thing. There is:

Single entry Non-o for supporting a Thai wife

Multiple entry Non-o for supporting a Thai wife

Extension of stay for supporting a Thai wife.