How long do I need to wait in Thailand before applying for a 30-day extension on my 60-day tourist visa?

You can apply for a 30-day extension on your 60-day tourist visa when you have 30 days or less remaining on your latest stamp at most immigration offices. However, some immigration offices, such as in Bangkok and Chiang Mai, may allow applications when there are 45 days or less remaining. Additionally, a few offices permit applications when you have about a week left.