It hardly comes as a surprise that the passed-over eldest son of Kim Jong Il has been criticizing hereditary succession.

In a soon-to-be-published book, “My father Kim Jong Il and Me,” Kim Jong Nam reportedly rails against the system in North Korea and calls his half-brother and current ruler, Kim Jong Un, a pawn of the ruling elite.

The book is based on a collection of interviews and emails between Jong Nam and Japanese journalist Yoji Gomi, who told the Telegraph that he built a relationship with Jong Nam after the pair met in Beijing in 2004.

GlobalPost in-depth series: After Kim Jong Il

Jong Nam has been spotted from time to time in Macau, where he lives in exile, and elsewhere in China. Usually, his name appears in the press next to the word "playboy."

Jong Nam reportedly told Gomi before Kim Jong Il passed away that North Korea was stuck. It needed economic reforms to survive. But those very reforms would lead to the collapse of the Kim dynasty.

More from GlobalPost: What's next for North Korea?

He wrote to Gomi on Dec. 17:

It is obvious that [the] economy will collapse without reforms, but the reforms will lead to a crisis of the collapse of the regime.

On Jan. 3, Jong Nam wrote more specifically about Kim Jong Un, who he said was merely a figurehead.

I question how a young heir with two years [of training as a successor] would be able to inherit ... absolute power. It is likely that the existing power elites will succeed my father by keeping the young successor as a symbol.

Sour grapes?

Word on the street is that Kim Jong Nam was once first in line to succeed his father, as birth order would suggest. But it wasn't meant to be.

In 2001, Jong Nam fell out with his father following an incident at Tokyo's Narita airport, where he was nailed for trying to get through on a fake Dominican passport. Jong Nam fled to Macau and has been living it up ever since.

And this isn't the first time some bitterness has surfaced from his direction. A few months ago, it was reported that Kim Jong Nam let loose on his Facebook page.

But expert North Korea watcher Bradley Martin said he there's more to it than sour grapes.

Martin thinks highly of Jong Nam. He wrote by email:

I think the real reason Jong Nam wasn't chosen to succeed was not so much his farcical Disneyland trip as his open recognition that the system needs to be changed. Last time I saw him quoted extensively he was not criticizing Jong Un but commiserating, offering to help.

GlobalPost's correspondent in South Korea, Donald Kirk, called Kim Jong Nam "an unguided missile" whose "uncensored, unauthorized comments provide relief from the relentless flow of propaganda."

The question is, according to Kirk, how long will the regime let him do it?

From Kirk's email:

The question is, how long he can get away with it before the regime finds a way to snuff him, or at least snuff his remarks. Clearly, as his remarks suggest, all is not as the ruling elite surrounding Supreme Commander Kim Jong Un would like the world to believe.

Jong Nam, now 40, is the son of the Dear Leader’s first wife. It isn't clear whether he attended the funeral for his father, but it seems certain that the inner circle in Pyongyang doesn’t want him getting anywhere near Kim Jong Un.

After all, like Jong Nam says, it's the elite surrounding Jong Un who pull the strings.