Short answers, pulled from the story.
Hiroshi Matsumoto drew the first version of Sagat in 1987. Character designer Akira Yasuda handled his design for Street Fighter II, and Naoto Kuroshima created the design for Street Fighter V under director Takayuki Nakayama.
Sagat received serious damage to one of his eyes during an early fight which resulted in partial blindness. He later challenged martial artist Gou Hibiki who purposely exploited this weakened eye and broke it completely during their match.
In January 2018, Saga Prefecture in Japan teamed up with Capcom to launch a promotional campaign called Street Fighter Saga. The collaboration included the opening of the Sagatto Shop in Tokyo's Ginza district to display local specialties to Thai visitors.
Real-life Muay Thai fighter Sagat Petchyindee has publicly claimed that the character was modeled after him based on his international popularity and eye injury requiring surgery. Despite these claims, Capcom has never officially confirmed the link between the fighter and the video game character.
Sagat develops a Tiger Uppercut similar to the attack that caused his chest scar from losing to Ryu. Their rivalry evolves into mutual respect when Sagat helps break Ryu free from M. Bison's brainwashing and proves there is still honor beneath his anger.