Elections in the Republic of Korea are governed by the Constitution, acts and decrees. The Constitution contains basic provisions regarding elections and includes the rights of citizens to vote and hold public office, along with fundamental freedoms of speech, press, assembly, and association. It also includes provisions for the elected offices and terms of office, presidential election, political parties and the creation of an election management body. The Constitution provides that elections should be conducted by universal, equal, direct, and secret ballot by the people.
Procedures, eligibility of voters and other concerns with regard to the electoral process are enclosed in the Public Official Election Act. The establishment of political parties and the multi-party system is provided by the Constitution and it is further governed by the Political Parties Act, which directs the participation of the parties in the electoral process. Another legal instrument used in the electoral process is the Political Funds Act, which is concerned with the fair provision of political funds, guaranteeing the transparency of and preventing irregularities concerning political funds.
Sources:
https://www.constituteproject.org/constitution/Republic_of_Korea_1987.pdf
http://aceproject.org/ero-en/regions/asia/KR/korea-republic-of-public-official-election-act/view
https://korea.assembly.go.kr:447/res/low_02_read.jsp
https://www.nec.go.kr/engvote_2013/main/download.jsp?num=598&tb=ENG_NEWS