Kings and queens are addresses as “Your Majesty” when speaking to them personally and all other members of the royal family would be addressed as “royal highness.” Upon second address, the queen should be called “m'am” and the king “sir.” The guidelines for addressing royals when writing to them does differ from the ...

How would you address a king?

When referring to a king, say, "His Majesty, the King." When addressing a queen, say, "Your Majesty, my Queen."

How do you respect the king?

Politeness reigns supreme. Follow common courtesy. Speak softly and don't laugh loudly. Treat bank notes bearing the king's image with respect.