"Dukes of Hazard" star John Schneider's Twitter fingers just landed him in a whole lot of trouble ... his recent call for President Biden's execution has now caught the attention of the US Secret Service.

A rep for the SS tells us they are aware of the comments Schneider made -- when he stated Biden and his son "should be publicly hung" -- and while they don't comment on "matters involving protective intelligence," the SS "investigates all threats related to our protectees."

You don't have to read much between the lines to figure out the Secret Service will certainly have a chat with Schneider in the near future.

As we reported ... Schneider tweeted a direct response to President Biden Wednesday, writing, "Mr. President, I believe you are guilty of treason and should be publicly hung. Your son too. Your response is..? Sincerely, John Schneider."

Biden's original tweet, which triggered Schneider's response, was about former President Trump, where Biden said, in part, "Trump poses many threats to our country: The right to choose, civil rights, voting rights, and America’s standing in the world."

Unclear exactly why Schneider decided to take down his tweet, but it was gone by Thursday.

In a statement to TMZ, Schneider tells us he, specifically, didn't call for an act of violence ... instead, saying, "Seriously, folks? I said no such thing. Despite headlines claiming otherwise, I absolutely did not call for an act of violence or threaten a U.S. president."