How can I change my METV to a Non-O visa for marriage while in Thailand?

The user seeks guidance on changing their Multiple Entry Tourist Visa (METV) to a Non-Immigrant O (Non-O) visa for marriage and dependents while in Thailand. Ubon Immigration informed him that he needs to open a bank account first, which he cannot do without a Non-O visa. Commenters suggest applying for the Non-O visa at the Thai Consulate in Savannakhet or another nearby country, as it cannot be done while remaining in Thailand on a tourist visa. They highlight that the application needs to be submitted in person, and note the requirement to have a certain number of days left on the current visa. They also advise him about the need to fund a bank account for an extension once he has successfully obtained the Non-O visa.