When is the earliest I can renew my non-O visa (marriage visa) before it expires, and how does the renewal date work?

You can generally renew your Non-O marriage visa 30 to 45 days before it expires, depending on the office. Bangkok, Chiang Mai, Phuket, and Buri Ram allow renewals 45 days prior, while other offices may permit renewal 30 days in advance. It's important to note that instead of renewing, you can apply for an extension, which will start from the previous visa's expiry date.