The speech did not mention clashes between riot police and mainly opposition activists that have taken place on an almost daily basis since martial law was lifted in May after government crushed a pro-democracy uprising.
The island nation, home to the US Fifth Fleet, is seen by the United States and Saudi Arabia as a key ally.
The amendments, which increase powers to question and remove ministers and withdraw confidence in the cabinet, emerged from a national dialogue King Hamad bin Isa Al Khalifa organised last year after the uprising.
The main opposition party Wefaq withdrew from the dialogue, saying it did not go far enough to offer real reform. The king, in a televised speech said: "Our people have proven their desire for continuing with reforms.
We complete the march today with those who have an honest patriotic desire for more progress and reform.
"I must mention here that democracy is not just constitutional and legislative rules, it is a culture and practice and adhering by the law and respecting international human rights principles," he said. "I beseech all sectors of society to work together so that all their sons adhere to the law."
The cabinet is headed by the same prime minister from the royal family who was appointed when Bahrain emerged from colonial tutelage in 1971. The elected parliament's powers to legislate are neutralised by an appointed chamber.
Copyright Reuters, 2012