Quentin Griffiths, the co-founder of the online fashion powerhouse Asos, has tragically passed away after a mysterious fall from an 18-story building in Thailand.

The 58-year-old millionaire was discovered dead outside a luxury hotel in Pattaya, a popular seaside resort, on February 9, as reported by the BBC.

Griffiths, a UK national, had been staying alone in his suite on the 17th floor, with the door locked from the inside, according to a police investigator speaking to the media.

Authorities noted there were no indications of forced entry or any signs of foul play. However, a comprehensive autopsy might take several months to complete, the Sun reported.

“It’s quite a mystery,” a source close to his family told the newspaper.

“The term ‘suspicious circumstances’ has been mentioned, but the details remain unclear at this point,” the insider added.

Police told the BBC Griffiths was involved in ongoing legal disputes that could have caused him stress.

He was separated from his second wife, a Thai national, who accused him of stealing more than $673,000 from the company they ran together, the Sun reported.

He was arrested last year and questioned by police after she alleged he forged documents to sell land shares from the firm without her knowledge.

He was released but the investigation was still ongoing at the time of his death, according to the Sun.

He co-founded Asos in London in 2000 with Nick Robertson, Andrew Regan and Deborah Thorpe. He left the company five years later, but remained a significant shareholder in the fashion and cosmetic retailer.

The business initially launched with the name As Seen on Screen, before switching to the Asos acronym in 2002.

It quickly skyrocketed and at one time was valued more than $8 billion, with Kate Middleton and Michelle Obama both wearing its own-label designs.