Heat corn oil in a large pot over medium-high or high heat for a minute. Add one kernel of popcorn to the oil. When the kernel pops, pour in the remaining popcorn and the vanilla bean. Place a lid on the pot, and shake gently until the corn starts to pop. Shake vigorously until the popping subsides.
Remove from the heat, and pour into a large bowl. Remove the vanilla bean from the corn. Scrape seeds from the vanilla bean, and mix with sugar. Stir sugar, salt and melted butter into the corn until evenly coated, and serve.