Danish officer in the Royal Siamese Gendarmerie, residing in Thailand from 1906 to 1947. He contributed to the modernization of the Siamese military through his service in the Provincial Gendarmerie. In addition to his military duties, Seidenfaden participated actively in the Siam Society. He pursued his interest in ethnology and authored several works, including books and articles about the history, culture, and languages of the Thai population.