The opposition Cambodia National Rescue Party boycotted Monday's 90-minute debate on the legislation and the subsequent vote that saw all 66 lawmakers from the ruling Cambodian People's Party vote in favor.
It now needs approval from the ruling party-controlled Senate, a simple formality.
Long-serving Prime Minister Hun Sen suggested the amendments earlier this month, in what is seen as an attempt to shore up his party's strength ahead of local elections this year and a general election in 2018.