What are the requirements to change my tourist visa to a Non-O visa based on marriage in Thailand?

find below the immigration website describing your plan. You case is number 6. Click on the text, open the pdf. It gives you all details on what to prepare for the application of the "change of visa type" from an exempt entry to the 90-days Non-Imm-O family visa. Keep in mind you are limited in time. You must deposit 400.000.- THB in your Thai bank account ASAP after you have arrived. You need a minimum 15 days left on your "admitted stay" stamp in order to be allowed to apply for the "Change". Visit immigration immediately and ask them for the handout of things you will need for the change. One thing is for sure: You must have a freshly printed Thai marriage certificate from the local Amphur. The visa will be given 15 days under consideration. After you have picked it up, you can apply for the "1-year extension of stay based on being married to a Thai wife" up from 30 days before the visa expires, and when the 400.000.- THB have sat in the account for 2 months. . . . . . . here's to ya: "6. Documents to be submitted for Change Visa – FOR PROVIDING SUPPORT TO OR BEING A DEPENDANT OF A THAI CITIZEN (SPOUSE VISA) (NON-O)" . . . . . . . .

400k in a Thai bank account is the main requirement. Easier to get the non imm o in your home country before you arrive!

You'll need a Thai bank account with 400k in ASAP to get the initial Non-O then season the money for 2 months to get the 12 month extension (if required). Were you married in Thailand?

What office are you intending to use? Best to ask them for the handout of requirements. Generally you’ll need to fill out a TM87 as you have an exempt entry but you’ll need other copies and stuff depending on that office.