BANGKOK — When the local fight legend Dejdamrong Sor Amnuaysirichoke walks into a packed arena here Friday, he will find much that is familiar, including the roar of his fans and the rhythmic “sarama” music that is an integral part of traditional Muay Thai kickboxing in this country.

But there will be one major difference: His fight will be the main event of the first major professional mixed martial arts event in Thailand, which for years had unofficially banned the sport in an effort to protect Muay Thai.

The fight night at Bangkok’s 11,000-seat Impact Arena, organized by the Singapore-based promotion One Championship, will culminate with Dejdamrong defending his M.M.A. strawweight title (52.3 to 56.7 kilograms, or about 115.3 to 125 pounds) against Yoshitaka Naito of Japan.

The nine-fight event, which also will include performances by two of Thailand’s most popular music groups, is sold out. It is being viewed as a test of both the popularity and the acceptability of M.M.A. in this country, whose sports authority in 2012 vowed never to support such an event because it was too violent and would smear the character of the popular domestic sport of Muay Thai.