He was a Muay Thai fighter in the early 1980s, and took the professional name Galaxy from a restaurant and nightclub owned by his manager's friend.

Due to he and his twin brother Khaokor Galaxy were born during the time that Pone Kingpetch, the first Thai world champion, was becoming famous.

Lacking the amateur boxing experience common to most Western professional boxers, Khaosai's skills originally were limited, and he relied on toughness and his fearsome punching power to win.

As he gained experience, Khaosai began to develop into a more refined boxer, learning combination punching to complement his deadly left.

Khaosai fought only once outside of Asia, when he defended his title in 1986 against unbeaten (and future WBA bantamweight titleholder) Israel Contreras in Curaçao.

He first took a shot at the music industry, releasing a single, "Khob Khun Krub", meaning "Thank You", then began taking part in TV series and movies, particularly comedies.

In 2005, while he was taking part in a film, he was punched in the face by a drunken fan, who wished to obtain Khaosai's shirt for collection but was denied.

The incident made frontline news, which displayed a photo of Khaosai, with a bandage on his face but smiling and standing next to the drunk man.

After retirement, he married the Japanese Yumiko Ota, whose he had met during a trip for his second fight with Kenji Matsumura in Kōbe, Japan in 1989.

[5] In March 2013, he made news again when he unexpectedly was married again, this time to Wannapa "Nung" Kamboonsri, before obtaining a legal divorce from his previous wife.

Additionally, during the 2011 Thai general election, he became a candidate on behalf of the Chartthaipattana Party for his native Phetchabun 2nd district, but lost with only 8,485 votes.