If Hitler was a POW, he would spent most of his time, painting and ranting about the Jews to anyone who would listen. Supposedly, he was a outcast in his unit for his anti-Semitism, so I doubt he would be a social butterfly as a prisoner of war.
Ironically, though, I think his anti-Semitism might win him a few friends among French officers, since if I recall correctly, anti-Semitism is still rife among French conservative circles. They may use Hitler as a stool pigeon, spying on his fellow prisoners. Now, this would make him even less popular among his fellow prisoners.
Assuming the war ends when it's supposed to, he is never recruited by Military Intelligence when word of his behaviour in the POW camp spreads around, which means he never joins the German Workers' Party. Chances are he would either become a artist or he dies in poverty. Either way, I don't see him becoming a politician.