Ngin's mummified body was found hanging behind the front door by a locksmith and the new owner of the flat, who had bought it at auction and had come to clear it out, according to Le Parisien newspaper.
Police say there is no doubt that he committed suicide eight years ago after being made redundant from his job as a security guard.
Ngin, who would have been 50 in a few days' time, lived in the town of Bussy-Saint-Georges, east of Paris, and played no part in France's Cambodian community.
He had two brothers and two sisters living in France but had cut off all contact with them several years before his death.
His neighbours assumed that he had returned to Cambodia but took legal action to recover unpaid communal expenses for the building, as did his bank for missed payments on his mortgage.
The action led to the apartment's sale at auction and, indirectly, to the discovery of the body.
Police say that Ngin suffered from obsessive compulsive disorder and had left the flat "hyperclean", meaning that his body was also well preserved and no suspicious smells leaked out.
"This is the tragedy of the greater Paris area, the possibility of being isolated in the middle of the crowd," a source commented to the AFP news agency.