Jose Canseco -- Threatens Magazine Publisher ... 'Pay Me $350k Or Else'

Jose Canseco is THREATENING the publisher of a popular lifestyle magazine ... claiming the guy owes him $350,000 ... and warns, "People get killed for less."

The man Jose is going after is Kamal Hotchandani -- the publisher and CEO of Haute Media Group ... which publishes Haute Living magazine, a lifestyle mag for rich people.

Canseco tells TMZ Sports the two were involved in a business transaction roughly ten years ago -- in which Kamal allegedly stiffed the ex-MLB star out of $350,000.

We reached out to Kamal and Haute Media several times to get his side of the story -- but haven't heard back.

Meantime, Canseco says he's run out of patience ... and tweeted, "Kamal hotchandani I am coming after you."

"Watch yourself kamal...yes that is a threat..you owe me 350k."

"Your time is up ..you should have contacted me now it's to late."

Canseco says he is NOT threatening violence -- he just wants to smoke Kamal out.

4:25PM PT -- We finally heard back from Kamal's camp -- and he ain't taking this thing lightly.

His attorney Sandy Becher tells us, "We have authorities in various jurisdictions dealing with Canseco's not only defamatory but downright extortionate and otherwise criminal behavior."

Becher says Canseco has been terrorizing Kamal with barrage of phone calls and texts -- and demands Jose cut it out, ASAP.

Becher continues, "Mr. Hotchandani categorically denies his flagrant lies and initially did not want to even dignify Canseco's false and inane accusations with a response, however he was left no other choice given the escalation in Canseco's threats against him and his family and irrational conduct but to seek the guidance of both state and federal authorities and pursue all civil and criminal remedies available at law should this conduct persist."