SEOUL — The vanishing act of Kim Jong-un provokes one inevitable question.

With all the billions that the United States puts into gathering intelligence by all those “agencies,” why can’t any of them come back with the definitive answer on the state of his health?

Just think about the multi-tentacle American intelligence apparatus sticking the noses of thousands of really bright, well-paid people into the lives of everyone on earth.

There’s the Central Intelligence Agency, the National Security Agency, the Defense Intelligence Agency — those are just the three best known of all the entities in and around Washington that are charged with finding out everything about everyone.

We may be absolutely sure they’re scrambling right now to discover Kim’s whereabouts, his condition, what’s ailing him so badly as to have laid him low — out of sight — for nearly three weeks. Oh, don’t worry, some people keep saying, he’ll show up any day ordering another missile test. Oh, say others, he’s obviously on life support, he’ll never walk or talk again.

The bottom line, as a lot of people honestly acknowledge with a shrug and a grin, is we just don’t know. Fair enough, but why can’t these expert analysts whose mission is to find the answers come up with anything? They should know definitively, and — considering how much taxpayers’ money goes into their “agencies” — we should know too.

The first question they need to figure out is where he is.

The initial report by Daily NK had him somewhere near Mount Myohyang, north of Pyongyang, where tourists are dragged to look at all the gifts that sycophantic visitors have bequeathed the kings of the Kim dynasty. Regime founder Kim Il Sung and his son, Kim Jong Il, didn’t know what the hell to do with all that bling so they put it on display as if to say, “Look how much everyone loves us.”

It’s been years since I visited Mount Myohyang on some group tour so I don’t know if Kim Jong-un, heir to all the country’s riches, has his own gift room there, but that Daily NK report had him sequestered in one of his villas nearby — after treatment for a cardiovascular problem in a hospital built specifically for members of the royal family.

Sounds good if true. Who knows? Not the CIA, for sure, and also probably not South Korea’s National Intelligence Service, whose ranks have thinned in three years of liberal governance under President Moon Jae-in.

Nor do we have any idea how or if Kim got to his great compound at Wonsan, the port on the east coast where he’s ordered construction of a great tourist complex. Satellite imagery put out by the Washington website 38 North showed a train at the station reserved for use only by Kim family members and friends and security people, but there are two problems with this revelation.

The first, as Jenny Town of 38 North tweeted after the picture had shown up everywhere, is the train may no longer be there. It’s not as though the satellite were stationary with the camera pointed all the time at that station.

The second problem, as the North Korean defector Thae Yong-ho, newly elected to the South Korean National Assembly has noted, is the wily North Koreans may have moved the train there just to fool everyone into thinking Kim must be in Wonsan. OK, why would they do that? Simple: they still want the world to think he’s all right, not laid up near Mount Myohyang.

But why  all the guess work and wild speculation?

Intelligence has improved in recent years with the ability to photograph just about every external detail from satellites, and electronic eavesdropping is highly sophisticated too. For that matter, the source in North Korea whom the website Daily NK credits with giving them the goods on Kim’s illness presumably used a mobile phone to call his contact in China or South Korea — a form of communications that would have been totally unavailable in years  gone by.

So what’s missing here? Human intelligence, humint, as they call it.

In all the decades since the Korean War, unbelievably, none of those huge, super-funded U.S. intel agencies have been able to seduce a single North Korean political or military figure who might know what he’s talking about.

Nobody in the Supreme People’s Assembly — much less the political bureau of the Workers’ Party, or, most likely target, the foreign ministry, with its missions abroad — has succumbed to the promise of a huge payoff and life ever after in the United States under an assumed name.

Surely it’s to the credit of those Kim dynasty regimes that they’ve so skillfully, brutally intimidated all those who might know anything to keep their mouths shut. That is, all except those who’ve been sending exclusive reports to President Donald Trump, who just said he does know how his friend is doing, “relatively speaking.”

Relative to what? “I can’t talk about it now,” said the Trumpster.

It is hoped he knows more about Kim’s health than he does about the medicinal effects of Lysol and Clorox on the coronavirus, but don’t count on it.