After 16 years, King will be allowed to come off contract at Leicester at the end of this month.
He penned a letter for the club's website, writing:
"To my LCFC family,
"Today it's been announced that I'll be leaving the Club and writing this was never going to be easy, even though I know it's been coming for a while now. After all, all good things come to an end, but what a journey it's been and I feel nothing but pride and happiness writing this statement.
"I came as a 16 year old boy in 2005 chasing a dream of playing one game of professional football for Leicester City. I leave a Premier League champion, having played 378 times. I've given you my all every time I stepped on the pitch and, in turn, the amount of love and support you've shown me over the years has been unbelievable. You've been there in the bad times and the very best times and I will never be able to thank you enough.
"I'm so happy the Club are allowing me the opportunity of showing my thanks to you at a later, safer date and that is something I'm already looking forward to. As a city, you've given me a life, a family and somewhere I now call home.
"There are too many thank yous to place on record however, I have to say how Khun Vichai changed my life. The way he transformed not only the Club, but the mentality of me as a player and a person is immeasurable. The same should be said for Top, who I have nothing but gratitude and respect for in how he has treated me since he arrived at the Club.
"To the lads, I can only thank you. It's been a joy to pull the shirt on with you and together we've achieved things many people thought not possible.
"The Club is an amazing place and I take great comfort knowing I've had the privilege of playing a very small part in that.
"I'm now looking forward to the future, I've still got huge desire to play at the highest level possible, both at club level and in my international career, and can't wait to see what the future holds.
"I look forward to seeing you soon and, from now on, I watch and celebrate on as one of you.