No worries,
posted by Paradise Jedaite in South Korea forum
Hey mate, I lived in Korea for 1.7 years on a tourist visa (however, I had to leave the country every 3 months) and I was working as a freelancer, from home.
No one's going to know what you're doing and most importantly, you're not working for a Korean company. You're working over the internet for a foreign company. There's no way you can get in trouble, so relax.
As long as the activities you engage in have nothing to do with Korea (working in a restaurant, cafe, etc) you're alright.
Cheers,
ionut