The world’s best-performing IPO stock this year is a little known Indonesian coal mining company that’s backed by one of Southeast Asia’s richest men.

PT Petrindo Jaya Kreasi has soared more than 2,900% since it listed in March following a $25 million offering. Yet it still has no analyst coverage, is richly valued and has relatively low trading volumes. Counting Indonesian billionaire Prajogo Pangestu as its main shareholder, the company’s market value has grown by more than 25 times to $5.4 billion in just nine months.

Indonesia has been one of the most vibrant markets for initial public offerings globally this year, partially helped by a boom in demand for renewable energy stocks. Petrindo, in particular, is among a cohort of Indonesian stocks that have posted unexplained gains and wild swings this year, reaping fortunes for their backers and leading to regulatory scrutiny.