The speaker starts out sounding like an all-powerful monarch. Everyone answers to him: kings, jesters, bandits, even children and animals. He has wives, kids, knights and thieves, and the whole world is his to shape. The list-like lines pile up quickly, which makes his power feel huge and exciting, and the easy "I laughed" suggests he's having a great time.
Then the last two lines flip everything. His mother yells, "Get off the computer John!" and we realize the kingdom was a game, most likely one where he builds or rules a world. The poem doesn't say which game, so that part is a guess from the clues. The speaker is probably a kid or teenager, and the humor comes from the gap between the grand fantasy and an ordinary house with a parent calling. The mood moves from playful and boastful to a gentle, slightly deflated comedy. There's also a small sadness: the control he enjoys on screen disappears the moment real life interrupts.