Supporters say the investment agreements will increase free trade, transparency and competition and provide protections for investors.
Since 2008, readership has fallen by as much as a half at some opposition-aligned papers.
The illness prevented Hun Sen from attending a number of meetings, including the 59th anniversary of the Cambodian People’s Party.
The former king visited Hanoi for 4 days, with his wife and the current king, his son, Norodom Sihamoni.
Hun Sen said the remarks were impolite and disrespectful following a 10-day visit this month.
Some 10,000 members gathered to mark 59 years since the party was founded.
An opposition lawmaker said Friday the response was inadequate because it did not go on to explain where the millions were spent.
Chhun Yasith, the head of the Cambodian Freedom Fighters, was sentenced to life in prison without parole in a US court on Tuesday.
The charge, for distribution of false information, carries a penalty of up to 15 years in prison.
The opposition party in recent months has been deeply critical of recent government efforts to mark the once-contested border.
Officials said the aid delivery was a routine part of bilateral ties between the two countries.
Chhun Yasith was a naturalized US citizen who fled Cambodia as a refugee in 1982.