Prayong Makkong started Muay Thai at the age of 13 at the Kor Srimongkon Gym where he took the name "Posai Saktuanchai".
[2] The apex of his career being the year 1977 where his domination led to the organisation of handicap fights where he had to take on multiple fighters in one night without a break.
The first time in Lumpinee Stadium against Jocky Sitkanpai and Jitti Muangkhonkaen who he defeated by decision.
[3] Later that year Posai faced three Japanese fighters in a row defeating all of them including one by knockout.
[4] During his best years as a competitor Posai scored wins over other notable fighters such as Neth Saknarong, Wichit Lukbangplasoi, or Sagat Petchyindee.