When is the best time to visit the BK immigration office for a short-term visa extension before expiration?

The best time to visit the Bangkok immigration office for a short-term visa extension is on a day that is not immediately next to a weekend or holiday, such as avoiding Mondays or Fridays. It is acceptable to apply for the extension as early as 5 days prior to the expiration date, although it's recommended to go when you have 45 days or less left on your current stamp. Be sure to bring necessary documents like your passport, TM30 form, and a passport photo.