you are completely mistaken. All they are asking for is proof that you are currently in the country of the Thai embassy that's processing your visa application. Nothing more, nothing less. Simply an entry stamp and proof such as your hotel booking or receipt.
don't know of any restrictions for European passport holders applying in Laos. Check their website visa services page. You just need to show your Laos entry stamp and your hotel booking to show proof you're in the country.
If you are legally married male and female then submit a new application referencing the main DTV holders DTV visa number or approval letter noting that this application is the spousal application with appropriate documents and pictures etc. refer to or ask the embassy or website requirements for such an application.
It means instead of walking in and applying and handing over your passport, you now apply online and get a PDF file to printout instead of an actual sticker visa. You state your current location on the evisa website and your application is directed to the appropriate embassy for processing.