경기도 고양시 일산동구 풍동 사서함 110-15호 신병교육대대 2중대 2소대 85번 훈련병 박정수 우편번호) 410-800

This is the address of the place where Teuk will be training in for five weeks, according to what I found in Tumblr.

According to the post, it'll take a week for the staff there to send the letters to him.

SO WRITE, WRITE, WRITE!

:D