From The Thaiger

The Thai embassy in Berlin says Thailand has been removed from Germany’s list of Covid-19 high-risk countries, according to a Thai PBS World report. Provided they are fully vaccinated with an approved vaccine, travellers from Thailand can now enter Germany without having to quarantine. The accepted vaccines are Pfizer, AstraZeneca, Moderna, and the Johnson & Johnson single-dose vaccine.

In addition to being fully vaccinated, arrivals from Thailand must produce a negative PCR test result, taken within 72 hours of travel, or a negative antigen test taken within 48 hours. Travellers who have recovered from Covid-19 need to show proof of a positive PCR test result that is at least 28 days old, but no older than 6 months, or evidence of being fully vaccinated with an approved vaccine at least 14 days before their arrival.

https://thethaiger.com/hot-news/tourism/germany-removes-thailand-from-its-list-of-high-risk-countries

I think this information is slightly incorrect. Vaccinated passengers coming from high risk areas don't need to quarantine provided they transmit prove of vaccination before arrival. So, regarding quarantine, there is not much difference between before and after removal for vaccinated people.

https://www.rki.de/DE/Content/InfAZ/N/Neuartiges_Coronavirus/Transport/Archiv_Risikogebiete/Risikogebiete_aktuell_en.pdf?__blob=publicationFile