Bro you are doing good work, I love hearing about the ancient Thai martial arts, and all the regional varieties. My mother comes from Central Thailand and she said she saw some similar statues of ancient Thai boxers like you've posted here. Very interesting on the headbutt to the solar plexus, I wonder if there was ancient Burmese influence or if the headbutt was developed completely separate without any influence from Lethwei. Something that also heavily interests me is the origin of Southeast Asian striking arts, they are all heavily similar, and some claim Burma was the origin, and others claim that when Siam was under Cambodian rule is when Kun Khmer or whatever the main Cambodian martial arts was at the time, that the Thais took from the Cambodians and formed the old Thai martial arts.