How can I extend a CY-3 visa and what is the required process?

The process to extend a CY-3 visa in Thailand generally involves obtaining proof of stay, which may include a TM30 registration from your landlord or equivalent documentation showing where you are residing. The comments indicate that issues with landlords not completing this registration are common, and some expats suggest checking into a hotel temporarily to acquire the needed documentation if your landlord is uncooperative. It's important to consult with the specific immigration office regarding their requirements, as practices can vary between different offices in Thailand.