Do I need to apply for an E-Visa before visiting the Thai embassy in Vientiane for a DTV Visa?

All Thai embassy visa applications are online, Vientiane however has in person payment in Thai baht only. On your evisa application form you can upload the passport page with your Laos visa and entry stamp. You can also provide the name of the accommodation you are staying at in Laos. Once inside Laos you can submit your application, download and print the QR CODE for payment and go to the consulate in Vientiane to pay. Do not go to the embassy, go to the consulate.

You cannot apply in person. E-Visa only

If you need faster and easier i recommend Jakarta :)

There is no appointment. All Thai embassies now use the e-visa system and that's where you will apply.

You can fill out the application online before traveling to Laos, but you cannot submit it until you've entered Laos and then also upload your passport page with your Laos entry stamp as proof of your location.

You'll then need to go to the embassy during specific hours to pay for your visa. After that you'll likely be contacted within 2-3 days to go to the embassy and have an interview. Once your interview is complete, most people report receiving their visa in 1-2 days.