Citizens of some countries do not need to apply for a visa for visits to South Korea of up to 90 days, these are listed at the website of the Republic Of Korea Ministry Of Foreign Affairs
If you wish to take up paid employment In South Korea you must apply for a work permit which is valid for employment from a sponsoring employer. For more details contact your nearest embassy of the Republic of Korea.
South Korea Working Holiday Visa Information
If you intend to visit South Korea, on holiday, a business trip, to study, work, volunteer or as an emigrant you should get up to date and accurate information from the official website of the Republic Of Korea Ministry Of Foreign Affairs