North Korean authorities were afraid that leaving behind any traces of their leader could bring his enemies to analyse them.
Lee Yun-keol, who worked in a North Korean Guard Command unit before defecting to South Korea in 2005, explained that using a toilet connected to public sewers could leave information about Kim’s health in the public domain.
He said: “Rather than using a public restroom, the leader of North Korea has a personal toilet that follows him around when he travels.
“The leader’s excretions contain information about his health status so they can’t be left behind.”
According to the former North Korean official, the dictator never leaves for a trip, even within his country’s border, without the portable toilet.
He uses a customised bathroom built in each one of his vehicles, including cars and personal train, South Korean news agency DailyNK claimed.
A source in South Pyongan Province familiar with Kim’s Escort Command told the DailyNK in 2015: “The restrooms are not only in Kim Jong-un’s personal train but whatever small or midsize cars he is traveling with and even in special vehicles that are designed for mountainous terrain or snow.
“There are multiple vehicles within the convoy so that people cannot tell which one he is in, and there is a separate car that acts as his restroom.”
The portable loo was just one of the many safety measures taken ahead of the meeting with US President Donald Trump.
Kim arrived in Singapore with two decoy planes to confuse ill-intentioned people, his bodyguards and his bullet-proof limousine, a £1.5 million armoured Mercedes Benz S600.
The leader also brought 20 more vehicles, including an ambulance.
And South Korean news agency The Chosunilbo said that when Kim arrived at the Changi Airport in Singapore this week on an Air China Boeing 747, he was accompanied by an IL-76 transport plane carrying food.
But he may not have consumed it, as during the historic summit the two leaders had a planned six-course working lunch, which included vanilla ice-cream for dessert.
The first-ever summit between a US President and a North Korean leader took place at the Capella Resort in Singapore, kicking off at 10am local time (2am GMT) and going on for more than three hours.
The meeting ended with an agreement that sees both sides committing to denuclearisation. Kim left the resort to head back to North Korea shortly after, while Mr Trump remained longer to hold a press conference.