He is a former three-division Rajadamnern Stadium champion who was famous during the 1980s and 1990s.
Rajasak started fighting in Muay Thai at the age of 14.
[1] In 1989 he defeated Ekaphon Chuwattana to capture the Rajadamnern stadium 115 lbs title.
[2] Rajasak became a successful fighter of the Bangkok circuit with his heavy knee style, he mostly fought for the promotor Klaew Thanikhul.
During his career he won the Rajadamnern Stadium belt at three different weights and defeated notable fighters of his era such as Langsuan Panyuthaphum, Jaroenthong Kiatbanchong, Therdkiat Sitthepitak, Robert Kaennorasing or Chamuekpet Hapalang.