Yes, I understand, but in France (at the Thai Embassy in Paris) you must submit your actual flight ticket and hotel reservation when applying for the visa. You cannot just provide tentative dates or sample flights.
From what I understand, a Thai visa is valid for 3 months. So if, for example, it was issued on September 1st, it would be valid only until December 1st.
But my trip starts on December 13th, which means I wouldn’t be able to enter Thailand anymore, even if I haven’t used the visa?