What would be the tax liability in Korea?

Scenario: Subject is a Spanish citizen (no other nationality). Learns Korean language in South Korea, staying in Korea with a D-4-1 visa (Student visa). The subject is not employee by any company (nor in Korea, either anywhere else). Subject does not have any other income otherwise.

However, the subject is director (owns 100% of shares) of a company in Hong Kong. The company does not pays the subject a salary, i.e. a salary as employee or for services. However, the company might pay the subject dividends. Dividends would not go to a bank account in Korea.

Question: Is the subject tax liable in Korea?
Question: What would be the way to calculate the amount of taxes? i.e. I assume below a given threshold the subject would be liable but would not have to pay any amount. So wondering what would be the calculation.
Question: How can the subject declare it,if required to?