Can I apply for a Thai DTV visa in Saigon after arriving in Vietnam on the same day?

When you go to Saigon (HCMC) you cannot apply in Hanoi, you have to apply in HCMC (Saigon), it never is a free choice.

Yes, you’ll need proof you legally entered Vietnam - usually a clear photo of your entry stamp works fine when submitting online. Many apply the same day they arrive. For locations: the Thai Embassy in Hanoi handles DTV applications, while Saigon has a Consulate. Some report smoother results with Hanoi, but technically you apply through the jurisdiction where you are. Just make sure your docs (especially passport photo + entry stamp) are crisp and legible.

Honestly, I’d recommend getting a solid guide before you go. You can check platforms like amazon, search for 'Thailand DTV Visa Guide. This helped me avoid small mistakes that could delay approval

Yes, I did that! I also put my hotel booking and receipt of a coffee in Hanoi next to my passport

Yes plus submit hotel booking.