What Does the Red Mark in a Passport Indicate in Thailand?

The red mark in a passport used by Thai Immigration can indicate several things. It could be a date stamp in red ink, sometimes also found in blue, which reflects the date of entry or the necessity to show a work permit for the Non Immigrant B visa. Other instances of red marks may signify a ban on entering Thailand or indicate that a visa is 'Used' or 'Invalid'. The meaning can vary, and it's important for travelers to understand the purpose of the stamp in their passport.