What is the procedure for transferring a Non Immigrant O visa to a new passport in Thailand?

To transfer your Non Immigrant O visa from your old passport to your new one in Thailand, you need to take both your old (invalidated) passport and your new passport to the immigration office that issued your extension. If you are still under the first 90-day stamp of an in-country visa, it cannot be transferred right away; you'll have to wait until you apply for a 1-year extension. Make sure to have any relevant documents, such as the visa transfer request letter if provided with your new passport. Bringing both passports might be necessary until the transfer is completed.