Moon began his weeklong trip Sunday with a state visit to Brunei, becoming the first South Korean head of state to make a state visit to the country in 19 years.
The trip later took him to Malaysia before it ended in Phnom Penh earlier in the day.
His departure from Cambodia came after a brief trip to Angkor Wat, an ancient Buddhist temple complex that makes up one of the world's oldest religious monuments.
The trip to Angkor Wat came at a request from the Cambodian government.
"Because Angkor Wat is a symbol of Cambodia's glorious ancient civilization and pride of Cambodians, (the president) agreed to accept the invitation to show his appreciation and respect," Moon's spokesman Kim Eui-kyeom said earlier.
Moon's first overseas trip in the year sought to improve his country's relations with ASEAN countries as the president seeks to greatly boost the country's economic and diplomatic relations with 10 member countries of ASEAN.
ASEAN countries, along with India, are key components of Moon's New Southern Policy that seeks to turn ASEAN into South Korea's next China.
Already, the 10 ASEAN member countries make up the world's second-largest importer of South Korean products after China.
Bilateral trade between South Korea and ASEAN reached a record high of $160 billion last year. Seoul seeks to boost the amount to over $200 billion by 2020.
Highlighting the importance of ASEAN countries to South Korea, Moon has pledged to visit each of the 10 ASEAN member states before his single five-year term ends in 2022. He has so far made bilateral visits to seven.
Moon will again preach the importance of cooperation between his country and ASEAN to open what he calls an era of Asia when he hosts a special South Korea-ASEAN summit, tentatively scheduled for November, partly to mark the 30th anniversary of the establishment of dialogue relations between South Korea and ASEAN. (Yonhap)