When is the best time to apply for a 30-day extension of a TR visa in Thailand?

The timing to apply for a 30-day extension of a TR visa in Thailand varies by location. In Chiang Mai, Buriram, Phuket, and Chiang Rai, you can apply with up to 45 days remaining on your current stamp. However, in Bangkok, you must apply with only 3 days remaining on your existing visa stamp. In most other areas, the application is accepted when you have 30 days left.