This is a really tough situation. A few years back we also found a hurt dog by the side of the road in an underpass, we thought he was dead until we saw his head move. He was aggressive and unapproachable, so we left food for a few days and an old blanket he could sleep on. On the second day he was already much improved because at first he couldn't even walk, but he was not safe on the roadside.
We got a Korean friend to call the city animal control-- I think every city has one, you should be able to find it listed on Jinju city's website, look for "유기동물" or "유기견" or another word for "stray animal" that you can find with a translator.
We were there to see animal control arrive because we had to meet the men and walk them to where the dog could be found. They came with nets and sticks and took the dog away in the back of a bongo truck. This didn't help to convince me I was doing the right thing. Much later I found out that the conditions at the city pound were more like Auschwitz than a shelter, so I never felt that I had really done right by the dog (who we called 'Foxy').
Animal control in Jinju may be an entirely different story, however, so it would be worth asking a Korean-speaking Jinju resident for advice on whether you should call them.
An alternative would be to search for rescue groups in or near your city. The
http://www.angel.or.kr/network.php website has some
URLs listed for Jinju here; this one looks like a rescue group:
http://cafe.naver.com/ssnnn1
If you have a Korean friend who can help you, give the rescue a call and see if they might have a humane trap and if they can recommend a vet who boards strays. Since he has a collar he may belong to someone who wants him back. But I guess the first step is just to catch him.
If you choose a DIY approach, I would start by leaving food for him in a dish, but without getting close to him. He may become friendlier with food to the point you can scoop him into a crate and get him to a vet yourself

But be very very careful, don't get bit or scratched.
Sorry I can't be of more help. Also, I'm closing the ARK discussion forums today (
more info here), so you won't be able to respond here. Sad to say as I am not a fan or a member of Facebook, but you will probably get more responses if you post your story
here.
Good luck to you! Thanks so much for helping this dog and not just passing him by. I wish there were more people like you in the world.