"Holidays" are truly referred to as "Days of Paid Leave".
Please note the only Statutory Paid Leave Day is Labor Day. A Statutory Paid Leave Day is one which must be given to the Employees, unless both parties consent to some other form of compensation, and is mandated by the Laws of the Republic of Korea. Christmas, Cheosuk and other days are not Statutory Paid Leave Days.
As such, unless stated explicitly in the employment agreement, if you do not work on those days they count towards your Paid Leave that you have accumulated over the year.
You accumulate 1 day per month, on average, and you are entitled to use the Paid Leave Days after your first year of service. If you do not use the days before the end of your employment the employer must pay you for the days not used.
Under the Labor Standards Act the Employer must provide 50% of the cost of Health Care Insurance if: 1) The company has more than 5 personnel (including the "Boss", part time drivers and cleaning staff) 2) If you work more than 15 hours per week.
Employers of Foreign Workers have additional requirements stated in the Immigration Act.