First off, the amount seized was not necessarily made in a year.
Second, most of the money would not make it to the Cambodian economy. It is likely laundered abroad. The whole operation is likely multinational, with only the workforce located in Cambodia.
Also keep in mind all the bribes, all the money laundering mentioned in the article by the 100s of affiliated subsidiares of the criminal group all in Cambodia
the big casinos which directly and indirectly support additional laundering
Second, most of the money would not make it to the Cambodian economy. It is likely laundered abroad. The whole operation is likely multinational, with only the workforce located in Cambodia.