Can I go to any immigration office in Thailand for a re-entry permit, and do I need an appointment?

You can typically go to any immigration office in Thailand to apply for a re-entry permit without needing an appointment. However, be aware that certain offices may have specific guidelines, such as requiring you to have previously obtained your visa extension, TM30, or completed 90-day reporting at that location. It's advised to arrive prior to lunch hours, as some offices, like the one in Central Festival Chiang Mai, only issue permits until noon. Make sure to bring the necessary documents, including a completed TM8 form, copies of your visa/extension, your latest entry stamp, a passport-sized photo, and the appropriate fee (1000 baht for a single re-entry, 3800 baht for a multiple entry).