[2] Following a disappointing showing at the IFMA 2012 World Muaythai Championships where he lost out to Vitaly Gurkov in the finals to take bronze, Kem returned to the professional ranks on September 28, 2012 when he defeated Thepsuthin Pumpanmuang, Prakaysaeng Gaiyang 5 Daow and Sirimongkol Sitanuparp, respectively, to win the Toyota Vigo Marathon 2012.
[9][10][11] He floored Mickael Piscitello with elbows numerous times en route to a unanimous decision win at Best of Siam 3 in Paris, France, on February 14, 2013.
[18][19][20] He beat Vahid Roshani by decision at MAX Muay Thai 5: The Final Chapter in Khon Kaen, Thailand on December 10, 2013.
[21][22] Kem lost the WBC Muaythai World Super Welterweight (-69.8 kg/154 lb) Championship when he was defeated by Vitaly Gurkov via decision at Ring Wars in Milan, Italy, on January 25, 2014.
[23] Kem competed in the welterweight (-70 kg/154 lb) tournament at Xtreme Muay Thai 2014 in Kowloon, Hong Kong on March 29, 2014, and was initially set to face Seyedisa Alamdarnezam in the semi-finals.