As the placard states, Nai Khanomtom is considered the father of muaythai (Thai boxing.) He lived during the 18th century, and is most famous for his defeat of between 9 and 12 Burmese Lethwei (or Let Whay, the Burmese style of boxing) fighters–depending upon the retelling of the story.
One account states that the Burmese king had Nai Khanomtom kidnapped after watching from afar as the Thai legend devastated one Burmese soldier after another in close quarters combat. Other accounts hold Nai Khanomtom was one of many Thai prisoners captured. By all accounts, Nai Khanomtom was pitted against multiple Burmese opponents–some of the best the country had to offer–in a boxing match and defeated them one after another without [significant] rest periods.
I probably should have posted this on March 17th, which is Thailand’s “Boxer’s Day” (not to be confused with the post-Christmas Boxing Day recognized in much of the Western world.)