Is it possible for a U.S. citizen in Spain to apply for a Thai DTV online or should I visit the consulate?

of course you can apply. Please only use the evisa portal. Tghe embassies are not equipped for this program (staff knowledge wise). and then just do some base research; who many people have applied from Spain, where is the closest embassy accepting applications for DTV near Spain, in Europe. A lot of people in the UK are getting approved within days. Yes, it is very easy from SEA, but its not impossible to do from any foreign country. Just make sure you can get to the interview if you are called in. But your location is not an issue unless 'it is'

You got this

Seeing as you have long term visa to stay in Spain you can apply online using the evisa system thru the Madrid consulate. Keep in mind they take a LONG time (up to 4 weeks) to process the application.

BUT

no issues applying thru them IF you indeed have a long term visa for Spain as a student

Fly to Vietnam or Taiwan on a one way ticket and apply online from there. Could take a couple of weeks at most, but that’s your best bet. If you have the income and time, it’s a good option. Make a vacation out of it.

The only way to apply is online. If your application won’t be accepted by the embassy in Spain, your best bet is to travel to a South East Asian country like Vietnam, Cambodia, Indonesia etc.

They accept applications from non residents.

You can see from many posts people apply in countries that they are just visiting. Several countries nearby Thailand which are easy to get the DTV from.

Don't go to the embassy in Madrid waste of time. Use the online evisa system

If you not Spanish citizen and don’t have resident permit in Spain your application will be rejected. Same policy in all Thai embassies across EU. Beside residence permit they will accept bank statements only from Spain or Andorra -visa?menu=5d7cf78c15e39c3e99d

Hy not check site of embassy? They write what is needed