Kwanthai Sithmorseng (, born August 18, 1984) is a professional boxer from Thailand. He fights in the strawweight division and is the former WBA Minimumweight World champion. He captured the title on November 5, 2010 by defeating fellow Thai Wicha Phulaikhao aka Pigmy Kokietgym and lost it on April 19, 2011 to Muhammad Rachman by KO.
He was born without ever knowing who his parents were. He entered the world of boxing by first going to watch a Muay Thai match and ended up following a group of fighters back to their camp. When the camp owner saw him, he decided to take him in and raise him. That was how he began his boxing career, starting with Muay Thai under the name Kwanthai Chor Nor Pattalung.