Scores of media organisations from around the world are already in Vietnam, watching his every move; Japanese and South Korean media outlets even sent reporters out to Chinese railways in a bid to catch a glimpse of Kim's armoured green train passing.
If Kim's smoke break was a moment of vulnerability, others showed Kim's power in a way that his carefully controlled image in North Korean state media might not allow.
When he completed its 3220km train journey in Dong Dang, a city on the Vietnamese border with China, the train initially stopped slightly too early for his door to line up to the red carpet, prompting a delay as the train shifted back into place.
And as Kim left the train to meet his Vietnamese hosts, an aide who appeared to be acting as an interpreter and was seemingly behind his cue, sprinted down to join him.
The North Korean leader then entered a Mercedes limousine, and bodyguards jogged by the vehicle's side as he waved to crowds, before driving on to Hanoi. But when the limousine arrived in the Vietnamese capital after a drive of several hours, some observers noticed that his vehicle had become grubby on the countryside roads.
The Trump-Kim summit is a diplomatic event, but it will also be a media spectacle. Kim's voyage by train appeared to be designed to invoke his grandfather's visits to the country, the most recent of which took place in 1964.
After he met with Trump in Singapore in June last year, North Korean state media released footage that showed off the lavish attention that Kim received from state signatories - but also featured lingering shots of the megacity's skyline, suggesting an ambition for North Korea's own economic reforms.
But media coverage of Kim from the outside world also places him under scrutiny. After Kim met with South Korean President Moon Jae In in the truce village of Panmunjom, South Korea's conservative Chosun Ilbo newspaper asked experts to look at photographs of Kim's shoes - ultimately concluding that a strange slope in the North Korean leaders heel suggested he was wearing custom heels and that he stood 1.64m, rather than 1.7m.
For Kim, it's possible that the international media attention is already a bit of a drag - and indeed, the Vietnamese Government may be keen to limit press access, too.
After it turned out that Kim was staying in the same hotel as the travelling press corps' media centre, the journalists were kicked out. A witness saw a North Korean official yell at the Vietnamese security staff, ordering them to stop journalists from photographing or even looking at Kim's entourage.
