Pak had been purged in January and was executed for "deliberately ruining the national economy" as a "son of a big landowner", South Korean media say.
They believe that Pyongyang needed a scapegoat for the botched revaluation of the currency - the won - which fuelled inflation and worsened serious food shortages.
The crisis threatened the smooth succession of power from the country's leader Kimg Jong Il to his youngest son Kim Jonh Un.
South Korean media reports suggest that Pak had submitted a paper claiming that a revaluation would "improve the people's lives and secure the national budget".
This caused Kim Jong Il to revalue the won in November, with people having to swap old bank notes for new ones at a rate of 100 to one.
Soaring prices after the revaluation proved Pak wrong. He was then reportedly denounced as a traitor at a party convention in late January and arrested on the spot.
In the capital Pyongyang shops which trade in won remain closed until next week when the revaluation is expected to be completed.
In the 1990s, a top agricultural official was publicly executed in North Korea following widespread starvation in the country.
France is to open an office in North Korea to support NGOs but will not open an embassy there, French Foreign Affairs Minister Bernard Kouchner announced on a visit to Tokyo Thursday.
France is the only European country apart from Latvia that does not have diplomatic ties with Pyongyang, because of Paris's criticisms of its human rights and nuclear policy.