How can I extend my stay in Chiang Mai for an additional 30 days, and do I need an appointment at the immigration office?

In Chiang Mai, you can extend your tourist visa by an additional 30 days with a walk-in appointment at the immigration office, meaning you don't need to schedule in advance. It's recommended to check the specific requirements for Chiang Mai, which may be similar to procedures in other locations like Phuket.