Movie from late 50’s or 60’s man is poor and walking next to a horse and when he wants eating from a basket of a horse he is getting caught by guards/police.
Poor man went to prison, the guards finding a proof of letter that he is a king.
But he is not a king he previously teared a letter without his name from a king.
Musical or movie, commedy
Can we rule out The Court Jester (1955)? https://www.imdb.com/title/tt0049096/
– celebes.warty.pigVerified, no that's not the right movie
– WarzX