How can I transfer my entry stamp to a new passport and apply for a tourist visa extension in Thailand on the same day?

To transfer your entry stamp to your new passport and apply for a tourist visa extension on the same day, bring both your old and new passports to the immigration office. At the Chaengwatthana office, you can handle both the stamp transfer and the visa extension at the same counter, and you only need to fill out a form for the stamp transfer. It's possible to get both done without an appointment, as they issue one waiting number for both services.