About 40 minutes before serving, heat the oil in a saucepan over medium heat. Add the rice and onion and cook until the onion is translucent but not brown, 5 to 7 minutes. Add the broth to the rice mixture along with the salt, chiles and corn and bring to a simmer. Stir well, scrape down the sides of the pan, cover and simmer over medium low heat for 15 to 18 minutes. The rice should have absorbed all the cooking liquid.