From FAIR:
But after passage of civil rights acts in 1964 and 1965, King began challenging the nation's fundamental priorities. He maintained that civil rights laws were empty without "human rights" -- including economic rights. For people too poor to eat at a restaurant or afford a decent home, King said, anti-discrimination laws were hollow.
...
King's economic bill of rights called for massive government jobs programs to rebuild America's cities. He saw a crying need to confront a Congress that had demonstrated its "hostility to the poor" -- appropriating "military funds with alacrity and generosity," but providing "poverty funds with miserliness."
How familiar that sounds today, more than a quarter-century after King's efforts on behalf of the poor people's mobilization were cut short by an assassin's bullet.
["The Martin Luther King You Don't See On TV", Jeff Cohen and Norman Solomon]
There's more, including mentions of King's "Beyond Vietnam" speech that I know I've never heard:
From Vietnam to South Africa to Latin America, King said, the U.S. was "on the wrong side of a world revolution." King questioned "our alliance with the landed gentry of Latin America," and asked why the U.S. was suppressing revolutions "of the shirtless and barefoot people" in the Third World, instead of supporting them.
In foreign policy, King also offered an economic critique, complaining about "capitalists of the West investing huge sums of money in Asia, Africa and South America, only to take the profits out with no concern for the social betterment of the countries."
You haven't heard the "Beyond Vietnam" speech on network news retrospectives, but national media heard it loud and clear back in 1967 -- and loudly denounced it. Time magazine called it "demagogic slander that sounded like a script for Radio Hanoi." The Washington Post patronized that "King has diminished his usefulness to his cause, his country, his people."