The poem is a short, chilling letter from a general who describes his job in three blunt steps: he kills, he writes, and he announces things with great praise. The title, "Public Relations," hints at what he's really doing. Violence is his duty, but the writing is a form of power too, because whoever tells the story shapes what people believe happened.
The line "Under the story of the king is the king" is the strangest and most revealing. It suggests the official story sits on top of a real person, and that the real person may be quite different from the praise. The general knows this, and he is the one doing the covering up.
The speaker sounds calm, even pleased with himself. He ends by repeating that the king calls him "a very knowing man," which reads as flattery, but also as a quiet threat: he knows too much. The mood is cold, flat, and uneasy, as though cruelty and spin have become ordinary office work.