Above table is Korean tax rate for Individual income tax as of now, minimum is 6% and 42% is the maximum, the local tax 10% of income tax will be added so actual tax rate would be 6.6% to 46.2%.
Flat tax rate for foreigner is 19%, so you need to add up 10% of the above tax for a local tax, and it'll be 20.9%, so it's a bit controversial among people complaining too much favor to the alien salaried man.
Tax rate will be multiplied to the tax basis, so actually it's lower than the above rate for tax payment.
To save tax, always try to keep a proper receipts(pay by check/credit card, tax invoice, cash receipts) for expenses(tax deductible items) and take care of dependents as well as donation amount to religious organization even if it's paid by your dependents.
For more details, please send me an email to firstname.lastname@example.org, gooday!