How soon can you extend a tourist visa after arriving in Thailand, and does it vary by immigration center?

The ability to extend a tourist visa in Thailand can vary significantly based on the specific immigration office you visit. Generally, most offices will allow you to apply for an extension when your arrival stamp has 30 days or less remaining. Some, like in Bangkok, Chiang Mai, and Phuket, might accept applications with up to 45 days remaining. However, certain offices, such as those in Jomtien and Samui, may only accept applications within the last week of your entry stamp. Always check with your local immigration office for their exact policies.