Late HM Sri Paanch Birendra Bir Bikram Shah Dev was one of the richest person on the planet (in terms of real assets)...but it kept decreasing as far as I have checked the records with other big ASSET heavyweights... If you leave out the Royals and Aristocrats...than I would think of some Rizal or one of the Marwari Nepali. But again, this is speculation as I haven't checked and verified the latest records.