How many days in advance can I request a 30-day extension on my visa in Thailand?

You can generally apply for a 30-day extension at immigration up to 30 days in advance. However, some locations like Bangkok, Phuket, and Chiang Mai may allow extensions up to 45 days ahead, while places like Pattaya may only accept requests up to a week in advance. It's recommended to check with your local immigration office for specific rules.