Former President Donald J. Trump, speaking at a multimillion-dollar fund-raiser on Saturday night, lamented that people were not immigrating to the United States from “nice” countries “like Denmark” and suggested that his well-heeled dinner companions were temporarily safe from undocumented immigrants nearby, according to an attendee.

Mr. Trump, the presumptive Republican presidential nominee, made the comments during a roughly 45-minute presentation at a dinner at a mansion owned by the billionaire financier John Paulson in Palm Beach, Fla., a rarefied island community.

Guests were seated outdoors at white-clothed tables under a white tent, looking out on the waterway that divides the moneyed town from the more diverse West Palm Beach, a mainland city, according to the attendee, who was not authorized to speak publicly about the private event but provided an extensive readout of Mr. Trump’s remarks.

Dozens of wealthy donors helped write checks that the Trump campaign and the Republican National Committee claim totaled more than $50 million, an amount that would set a record but had not been verified. Campaign finance reports encompassing the date of the event won’t be available for months.

Some of Mr. Trump’s comments were standard fare from his stump speeches, while other parts of the speech were tailored to his wealthy audience.

About midway through his remarks, the attendee said, Mr. Trump began an extensive rant about migrants entering the United States, at a time when President Biden has been struggling with an intensified crisis at the Southern border.