The correct order is the following.
We are talking about social classes during the feudal system in the European Middle Ages. So the classification was the following.
At the top of the pyramid, was the king, followed by the nobles, then the knights and vassals, next, farmers, merchants, and craftsmen. And at the bottom of the pyramid, peasants, and serfs.
The feudal system worked out well during the Middle ages in Europe. It protected people who were dedicated to doing their jobs, meanwhile, the nobility tried to exert its power and influence on the king and the pope.