President Yoon Suk Yeol and first lady Kim Keon Hee greet officials as they leave for the Philippines at Seoul Air Base, south of Seoul, Sunday. Yonhap

President Yoon Suk Yeol left for a three-nation Southeast Asia trip Sunday that will include state visits to the Philippines and Singapore and then a trip to Laos for an annual summit led by the Association of Southeast Asian Nations (ASEAN).

On the first leg of the six-day trip, Yoon will arrive in the Philippines on Sunday where he will meet with President Ferdinand Marcos Jr. to discuss ways to enhance bilateral relations, especially as this year marks the 75th anniversary of diplomatic ties between the two nations.

On Tuesday, Yoon begins a two-day state visit to Singapore, where he will hold bilateral talks with Prime Minister Lawrence Wong to deepen economic ties in areas of artificial intelligence, digital, defense and supply chains.

In Singapore, he plans to deliver a speech on South Korea's unification vision on Wednesday.

On Thursday, Yoon will attend the ASEAN summit, during which Korea will elevate its relations with the 10-nation regional bloc to a comprehensive strategic partnership, and participate in the ASEAN Plus Three summit involving South Korea, Japan and China.

In a written interview with the Associated Press, Yoon said he will highlight North Korea's recent disclosure of a nuclear facility, which he believes is aimed at drawing the U.S.' attention ahead of next month's presidential election, while warning of its potential provocations, such as a nuclear test and a long-range missile test.

"At the upcoming ASEAN-related summits, I will stress the importance of denuclearization of North Korea, which is a prerequisite for realizing a free, peaceful and prosperous Indo-Pacific region," Yoon said in the interview with AP.

"This will serve to send a clear message that the international community will never condone North Korea's reckless actions," he said.

Yoon said he will seek to further expand cooperation with ASEAN on a range of areas, such as politics, military exchanges, cybersecurity, the environment and a safety net against financial crises, according to the interview.

Talks have been under way to arrange Yoon's first in-person meeting with Japan's new Prime Minister Shigeru Ishiba in Laos on the sidelines of the ASEAN summits, a presidential official told reporters.

On Friday, he will participate in the East Asian Summit, a regional security forum, and return home. (Yonhap)