I asked the airline the same question a few years ago when I was traveling on business, and the response was as follows:

Transfers of less than 6 hours are not allowed to leave the airport, and you need to wait in a designated area. So a visa is not required.

If the connecting flight is within 6-8 hours, KAL will provide free meals;

If the connecting flight is within 8-24 hours, KAL does provide free meals and accommodations, which are uniformly sent to the hotel by bus. Once you get to the hotel, you can go out and have a look around.

The transfer time is more than 24 hours, this must apply for a visa.

It is recommended to ask KAL if there is any change in the above rules.