Moon, a former human rights lawyer and leader of the liberal Democratic Party, promised change in several areas of domestic and foreign policy.
He pledged to reassess the controversial deployment of the US-built Terminal High Altitude Area Defense (THAAD) anti-ballistic missile system in South Korea, which is a source of conflict with Beijing.
Amid rising tension between the US and North Korea over the latter's nuclear weapons and ballistic missile development, Moon has called for negotiations with Pyongyang and said he would be prepared to travel to Pyongyang for talks "if the conditions are right."
Domestically, the new President proposed a more socialist program of reform than his predecessors and calls for higher taxes, salaries and pensions; he opposes nuclear and coal energy. Some observers have even called him the "South Korean Bernie Sanders."
Artem Lukin, Associate Professor at Far Eastern Federal University's Department of International Relations, told RIA Novosti that if Moon can make good on his promises, regional cooperation will benefit.
"He [Moon Jae-in] pays a lot of attention to the development of economic cooperation with North Korea as well as links with Russia. With the election of Moon Jae-in, the prospect of tripartite economic projects on the Korean peninsula is somewhat improving. Moon Jae-in advocates diplomacy over the conflict with North Korea, as does Russia," Lukin said.
Bilateral trade between Russia and South Korea was worth $25.6 billion in 2014, and it is one of Russia's most important trading partners in East Asia, after China and Japan. On the other hand, Russia is South Korea's 11th most important trading partner and 9th biggest exporter.
Professor Alexander Latkin, Director of the Institute of International Business and Economics at Vladivostok State University of Economics and Service [VSUES], said that there is already a good basis for further development of economic relations between South Korea and Russia's Primorsky Krai.
"There are a lot of successful projects, for example the Hyundai hotel in Vladivostok. They are constantly offering new projects, the flights have become regular, there are now three flights a day from Vladivostok to Seoul, plus ferries," Latkin said.
However, optimism about better relations with South Korea should be tempered by an understanding of the political situation there, which leaves the new President with "limited room to maneuver," Lukin said.
"Under any President, South Korea has to reckon with the opinion of its senior ally, the US. Besides, the South Korean establishment hasn't gone anywhere and also won't allow Moon Jae-in to radically change its foreign policy course towards North Korea," the analyst cautioned.