When can I apply for the extension of my NON O (marriage) visa before it expires?

You can apply for a year extension of your NON O (marriage) visa 30 to 45 days before it expires, depending on the immigration office you choose. Most offices allow applications 30 days in advance, while some major offices like those in Bangkok and Phuket may allow applications 45 days prior. It’s advisable to confirm with your specific immigration office regarding their policies.