How can I extend my Thai tourist visa from 60 days to 90 days, and when should I apply?

To extend a Thai tourist visa from 60 days to 90 days, you can typically apply as close as one day before your current visa expires. However, it's generally recommended to approach the immigration office within 7 days before the expiration. Required documents include a TM30 form, a passport photo, and a copy of your passport. Be sure to check for any public holidays that might affect processing times.