Can I reschedule my DTV interview appointment due to an urgent business meeting?

If they didn't reply you then it means they can't reschedule. By claiming u got an urgent meeting in Thailand is going to bring your application to get rejected, u can't conduct any sort of physical business in Thailand, even with the DTV. Is that meeting more important than 10k spent for the application? If yes then go for it and then apply again in Vietnam otherwise u just move your meeting

Did you also try to contact the Thai Embassy in Vientiane via Facebook or Facebook Messenger??

An urgent meeting shouldn't happen as you're supposed to be a digital nomad and can't conduct business in Thailand. It would then be better if you wait in the country of application and request an online business meeting instead.

Personally, i would give the benefit of the doubt to the Anonymous OP and say the urgent business meeting is not in Thailand nor Laos, but somewhere else

As for it being in-person meeting versus virtual meeting via Zoom, Webex, or other platform; well, being a digital nomad, remote worker, freelance drifter, etc. sometimes having a face-to-face meeting is beneficial

DTV means you are a digital nomad, therefore you do not work in Thailand. Therefore any urgent business meeting would be online, not in person. If you are saying to the embassy you need to return to Thailand for an urgent business meeting, you are putting a red flag on your application

How come they can request interviews for some People?

Is it when they are suspicious as to whether your doing legitimate work or not?

It's very unusual that the appointment is next week, because you usually get an email in the afternoon and have to show up for the interview the next day. The appointments are scheduled at such short notice so that people who are already back in Thailand don't have the opportunity to travel to Laos so quickly. What I also find quite strange is that there's a counter where you can pay the 10,000 baht every morning. You must know this counter because you paid the 10,000 baht there. So why don't you just go there and talk to the person at the counter? That makes the most sense. Something is not right about your story.

I would suggest waiting for the interview at the embassy first, as the visa will likely be approved shortly after the interview. However, if it really doesn't work out, you may need to email the embassy.

Alternatively, you could consider postponing the meeting plan.

I hope this helps you in some way.

You mean you want to leave Vientiane, go to the meeting (Thailand) and then return later to Vientiane for the rescheduled interview? Good luck with that!