Are you able to get your visa (and COE) from a country, let's say Belgium, and depart from another country for instance the Netherlands or Germany?
TLDR : Answer Summary
Yes, it is possible to obtain your visa and Certificate of Entry (COE) from one country (e.g., Belgium) and depart from another country (e.g., Netherlands or Germany). However, if you are considering participating in the Sandbox program in Thailand, it is important to verify that both departure countries are classified as low or medium risk.