Test results were also negative for 11 people, including one Indian and five Koreans, who came in close contact with Park Soon Hum. The 64-year-old man was an expert with Chosuk Construction & Development Co., Ltd. at Nghi Son-Thanh Hoa Economic Zone.
Doctors say they will continue to monitor those who worked with him.
Park, who entered Vietnam in January, was found dead in the company's bathroom on June 10, Ha Dinh Ngu, director of Thanh Hoa's Health Department, said.
He had symptoms like fever and cough since June 6, but did not visit any doctor, Ngu said.
Park's son, who is a doctor in the RoK, reportedly said that he could have died from a stroke and that he had diabetes.
Falling in the same group of viruses as the common cold and severe acute respiratory syndrome (SARS) which killed 800 people around the world in 2002-03, the Middle East Respiratory Syndrome coronavirus (MERS-CoV) was first reported in Saudi Arabia in September 2012.
The World Health Organization has since been notified of 1,227 laboratory-confirmed cases of infection with the virus, including at least 449 related deaths.
The RoK has seen the largest outbreak of MERS outside Saudi Arabia with 126 reported cases, including 11 deaths.
The virus causes symptoms like cough, fever and shortness of breath, and is highly fatal – 36% of MERS patients have died, according to WHO.
No vaccines or treatment is available for MERS, whose route of transmission still remains unknown, though most cases are attributed to human-to-human infection, it said.