Before he was arrested last month for allegedly running what’s likely the world’s largest cybercrime computer network, Wang YunHe enjoyed a lavish lifestyle in Singapore.

He held a bank account in the city-state, was a director of several local companies and lived in a multi-million-dollar apartment overlooking a premier shopping district, according to an indictment and local filings. All the while, the 35-year-old Chinese national was amassing riches by offering cybercriminals access to millions of infected devices for a fee, the U.S. Justice Department said.

The case is putting a fresh spotlight on the challenges of policing the influx of foreign wealth into Singapore, less than a year after 10 people of Chinese origin were charged in the nation’s biggest biggest money-laundering scandal.