He became Dutch Champion winning all of his fights in all the weight classes. At just 16 years old he won his first A-Class MTBN Title match and Souwer held three different World titles at 18. He won the S-Cup 2002 shoot boxing competition in Japan and made his K-1 debut in 2003 and won his first K-1 World Max championship in 2005. As of December 2014 his kickboxing record is 153 wins, 15 losses, and 1 draw. In March 2014 he made his professional boxing debut defeating Paata Varduashvili.