South Korean officials believe the escapee might have managed funds for Jang Song-Thaek, who until this week was regarded as Kim's political regent, said the South's cable news network YTN, citing intelligence sources.
The report also said he may have information on secret funds controlled by the Kim family.
It said the man escaped from Pyongyang two months ago and is now under the protection of South Korean intelligence agents in China while he awaits a flight to Seoul
The South's National Intelligence Service (NIS) told a parliamentary committee Tuesday that it believed Kim's uncle Jang had been removed and two associates executed.
YTN said the aide fled after discovering Jang's dismissal.