Short answers, pulled from the story.
Sagat was conceived by Takashi Nishiyama and designed by Hiroshi Matsumoto, also known as Finish Hiroshi, the designer of the original Street Fighter game. Matsumoto drew inspiration from Kickboxing and Muay Thai films that were popular at the time of the game's development.
Sagat's chest scar was added in Street Fighter II to represent his earlier defeat at the hands of Ryu. Animator Hiromi "Mori" Kotobuki suggested the scar, and character designer Akira "Akiman" Yasuda described it as a way to build Sagat's narrative role as a returning rival. The scar was caused by Ryu's Shoryuken.
Sagat stands 226 centimeters tall, which is 7 feet 5 inches. His imposing height is a central element of his character design and contributes to his intimidating screen presence.
Sagat was portrayed by Wes Studi in the 1994 live-action Street Fighter film.
Real-life Muay Thai fighter Sagat Petchyindee has publicly claimed the character was modeled after him, citing his name, his international fights in America and Japan, and an eye injury that required surgery. Capcom has never officially confirmed the connection, and journalist Sergio Hidalgo noted major physical differences between Petchyindee and the character.
Street Fighter Saga was a promotional campaign launched in January 2018 as a partnership between Saga Prefecture and Capcom, celebrating the 30th anniversary of Street Fighter II. Sagat was the central figure, chosen for his popularity and the similarity between his name and the prefecture's name. The campaign included the Sagatto Shop in Tokyo's Ginza district.