Rob was born "Saiyan Prakhantree" in Nong Khai, a city in Northeastern Thailand on the border of Laos, but grew up in Ban Phue in the province of Udon Thani. Rob first saw Muay Thai on television when he was 4 years old, and later, went to see live fights near his home. At age 11, Rob started thinking seriously about becoming a fighter for a profession, but his parents insisted that he stick to his studies. Rob repeatedly asked his mom to take him to a gym to study Muay Thai, and the answer was always no. But Rob wouldn't give up on his dream.

When Rob was 13 his older brother secretly took him to compete in an amateur fight near his home. Rob had no formal training, and stepped into the ring with an already experienced fighter. Rob lost but was more determined than ever to train in a real gym and fight professionally. A couple months later, Rob was visited by a childhood friend who was training in the Fairtex Muay Thai camp in Bangkok. They snuck out of their homes to go to Bangkok, where he would finally start to live his dream.

Rob was ranked in the top ten at the Lumpini Boxing stadium and he is immensely proud of the status he achieved in his career, the pride he brought to his family and his ability to help his family financially to lessen the burden of making a living in rural Thailand.