So far, North Korea has dominated the discussions, but trade has been at or near the top of Mr Trump's agenda, as China's economic influence in Asia is growing while that of the USA appears to be ebbing.
"Family by family, city by city, the people of South Korea built this country into what is today, one of the great nations of the world. Trade has become a very important element of our relationship".
President Trump's last stops in Vietnam and the Philippines proved the most problematic.
Trump and Quang also discussed North Korea and the South China Sea.
"South Koreans saw the world being reminded that the North Korea issue is a global problem the entire world community - including China and Russian Federation - will need to come together to solve", he said. Safety and security are goals that we can progress, not provocation. We don't want that.
A November 12 Tweet by Trump might point to Trump's change in strategy.
Mr. Trump said the pomp and pageantry of his Chinese welcome was a proper tribute for him and for the U.S.
On Friday in Vietnam, after cozying up to the Chinese leadership, Trump pivoted, taking a hard line against Chinese trade practices in a speech to CEOs attending the annual Asia-Pacific Economic Cooperation summit.
What was apparent during the trip was that Trump did not feel above jumping into the sometimes idiosyncratic traditions of these global summits.
"I don't blame China". "We know already that Donald Trump is attracted to strong men, he's attracted to people who exhibit these sort of authoritarian or even fascist tendencies".
"I also have come here to this peninsula to deliver a message directly to the leader of the North Korean dictatorship: The weapons you are acquiring are not making you safer".
In South Korea, he was treated to clamorous applause during a parliamentary address, on the first state visit by a USA leader in a quarter of a century.
Business deals announced by the president are tentative agreements that may not be fulfilled.
Trump told the APEC CEO Summit that he is willing to make bilateral trade agreements with any country in the Indo-Pacific region, but he firmly rejected multi-national deals such as the 12-nation Trans-Pacific Partnership, which was quickly abandoned in the first days of his administration.
Chinese President Xi Jinping told the summit in Vietnam that Asia-Pacific nations must "uphold multilateralism", countering Trump's message that the U.S. would stay out of trade deals that surrender its sovereignty.
"We will no longer tolerate the audacious theft of intellectual property".
"From this day forward we will compete on a fair and equal basis", the president said.
From now on, however, Trump warned the United States will, "expect that our partners will faithfully follow the rules".
"President Xi I think is going to be a tremendous help ..."