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.

“These are people coming in from prisons and jails. They’re coming in from just unbelievable places and countries, countries that are a disaster,” Mr. Trump told his guests, according to the attendee. The former president has made a similar claim the heart of his campaign speeches.

He then appeared to refer to an episode during his presidency when he drew significant criticism after an Oval Office meeting with federal lawmakers about immigration during which he described Haiti and some nations in Africa as “shithole countries,” compared with places like Norway.

“And when I said, you know, Why can’t we allow people to come in from nice countries, I’m trying to be nice,” Mr. Trump said at the dinner, to chuckles from the crowd. “Nice countries, you know like Denmark, Switzerland? Do we have any people coming in from Denmark? How about Switzerland? How about Norway?”

He continued, “And you know, they took that as a very terrible comment, but I felt it was fine.”

Mr. Trump went on to say that there were people coming from Yemen, “where they’re blowing each other up all over the place.”

During his rallies, Mr. Trump frequently laments migrants from a list of countries from Africa, Asia and the Middle East as he stokes fears around the surge at the border, which he blames for a spike in crime, blame that has not been supported by available data.

At the dinner, Mr. Trump also lamented the surge of migrants, particularly from Latin America, saying that gang members “make the Hell’s Angels look like extremely nice people.”

“They’ve been shipped in, brought in, deposited in our country, and they’re with us tonight,” Mr. Trump said.

“In fact, I don’t think they’re on this island, but I know they’re on that island right there. That’s West Palm,” Mr. Trump said, gesturing across the water, according to the attendee. “Congratulations over there. But they’ll be here. Eventually, they’ll be here.”

Asked to comment, a Trump campaign official pointed to an official readout of the former president’s event, including that he had discussed the border crisis and the tax cuts that he enacted while in office. The official did not address the specific quotes and did not respond to a question about whether the campaign was disputing them.

Mr. Paulson’s estate sits along the waterway that separates the town of Palm Beach — a wealthy community on a barrier island that, according to the Census Bureau, is 93.8 percent white — from West Palm Beach, where nearly a third of residents are Black and a quarter are Hispanic.

Mr. Trump blamed his successor, Mr. Biden, for the influx of migrants and mocked him and aides for what Mr. Trump said were bad decisions made around the Resolute Desk, which has been used by two dozen presidents.

“The Resolute Desk is beautiful,” Mr. Trump said. “Ronald Reagan used it, others used it.”

He then denigrated Mr. Biden, sounding disgusted, according to the attendee: “And he’s using it. I might not use it the next time. It’s been soiled. And I mean that literally, which is sad.”

The attendee who witnessed the moment said that dinner guests laughed and that Mr. Trump’s remark was interpreted as the former president saying that Mr. Biden had defecated on the desk.

Mr. Trump also sought to point to parts of his record that could appeal to the wealthy donors in attendance. He highlighted the tax cuts under his administration and asked attendees about whether they had a preference for that measure or his regulations that allowed them to take advantage of specific write-offs, according to the attendee.

“The most successful people in the whole country are in this room,” Mr. Trump said.

He ended his remarks with a grave assessment of America’s future that has characterized his campaigns for the presidency, but with a more apocalyptic tenor in 2024.

“This could very well be the last election this country ever has,” Mr. Trump said, using a line that has become standard at his rallies. “July 4 is not as important as this as far as I’m concerned.”