Warm the vegetable oil in a large soup pot over medium-high heat. Season the diced chicken with seasoned salt and black pepper, then add it to the pot. Cook, stirring occasionally, for about 5 minutes or until the chicken is fully cooked and no pink remains.
Add the chopped onion to the pot, cooking until it turns nearly translucent, about 5 minutes. Stir in the minced garlic and cook for an additional 2 minutes, or until the garlic is lightly browned and fragrant.
Pour in the chicken broth and water, followed by the sliced potatoes, chopped carrots, and celery. Bring the mixture to a gentle simmer, allowing it to cook for 15 to 20 minutes or until the potatoes and carrots reach desired tenderness. Adjust seasonings as needed with salt, black pepper, and cayenne for an extra kick.