Can I extend my 60-day tourist visa in Koh Samui early, and how does it affect the expiry date?

The user is inquiring about extending their 60-day tourist visa while in Koh Samui, specifically if they can do this a month early and how the new expiry date will be calculated. From the comments, it's confirmed that the extension can be done now, and the additional 30 days will be added to the current expiry date, extending it from the initial 60 days without needing to wait until the visa expires.