The 20-year-old speaking at the club's Lennoxtown training complex before joining in his first training session for the club, knows he has to hit the ground running if he is to feature for his country in South Africa in the summer.
"It is very important for me to be playing regularly, otherwise my manager at South Korea is not going to be too happy," the Young Asian Player of the Year said.
"I join Celtic in January and that means there is not much time.
"The manager (Tony Mowbray) is gambling also because he doesn't know much about me.
"But it won't take a long time to settle in and I am confident that I can show the fans and players what I am capable of, so it is not a big problem.
"I am really looking forward to the World Cup, it is my first one and it will be a good experience to be playing against the best players in the world."
Ki, however, all but ruled himself out of an Old Firm derby debut against Rangers at Celtic Park on January 3.
"I haven't trained for a while so I need a couple of weeks to build my body," he said.
"In my opinion, I'm not ready for the Old Firm game but if the manager wants me to play then maybe I will be get an opportunity.
"I have watched a lot of Celtic versus Rangers games and so it will be very interesting, with a lot of pressure.
"Korea and Scotland have totally different styles of playing.
"I need to be stronger and I need to improve physically and technically.
"I have a long way to, I am only 20 and have about 15 years ahead of me.
"Maybe in two or three years, I will be better than I am now.
"But I don't think it will be a problem to adapt."