Tiongson was a Visiting Professor at Osaka University of Foreign Studies in Japan; and Fulbright Visiting Professor at the University of California, Berkeley; University of Michigan; University of California, Los Angeles; and University of Hawaii at Manoa. Tiongson also received an Australian Cultural Award for his extensive research on Philippine culture , resulting in two pioneering works on Philippine drama: Kasaysayan at Estetika ng Sinakulo at Ibang Dulang Panrelihiyon sa Malolos and Kasaysayan ng Komedya sa Pilipinas.
Tiongson was vice-president and artistic director of the Cultural Center of the Philippines (CCP) from 1986 to 1994. He conceptualized a new direction for the CCP, in 1986, and subsequently authored a comprehensive cultural development plan that has broadened the scope of the CCP Outreach Programs nationwide. He paved the way to give more opportunities and recognition for regional artists and arts organizations through productions, conferences, forum-lectures, publication and research. He continuously writes history and criticisms about local arts and culture that serve as reference materials of scholars, researchers, academicians, and young students of the present generation.
Tiongson was also the Philippine Director of Sangandaan 2003, a cultural commemoration that highlighted the arts and media produced by Filipinos, Americans and Filipino-Americans in the course of Philippine-U.S. relations from 1899 to 2002. The cultural events were commemorated in the Philippines on July 6-30, 2003 under the sponsorship of the University of the Philippines, the Cultural Center of the Philippines and the San Francisco State University, in collaboration with numerous public and private institutions in the Philippines such as the National Commission for Culture and the Arts, the National Historical Institute, the National Library, the National Museum, the Metropolitan Museum of Manila, Ateneo de Manila University, and De La Salle University-Manila, and in the United States such as the City College of San Francisco, and the University of San Francisco.
During his short term as Director of the Movie and Television Censorship and Review Board (MTCRB), Tiongson played an important role in the controversy surrounding a film popularly known as Live Show. The film, directed by Jose Javier Reyes, focused on performing women and men who engaged in sex acts onstage at some night clubs in the Manila area. The film was accepted for exhibition at the prestigious Berlin Film Festival. On March 22, 2001, the Philippine Daily Inquirer noted: "Reyes believed the film illustrated the depressing lives of people forced through poverty to engage in the sex trade." Live Show was banned after Manila Archbishop Jaime Cardinal Sin denounced the film and labeled it as "immoral" and "in violation of the campaign for moral reform." Tiongson resigned shortly after Philippine President Gloria Macapagal Arroyo banned Live Show, and noted his conviction that the President had been pressured by influential Filipino members of the Catholic Church.
Tiongson has taught Philippine literature, theater, and general culture at the University of the Philippines, the Ateneo de Manila University, De La Salle University-Manila, the University of Hawaii and the Osaka University of Foreign Studies. He also taught Filipino and Philippine literature at the College of Arts and Letters, University of the Philippines from 1974 to 1986. Among the books he edited are: The Cultural Traditional Media of ASEAN, The Urian Anthology, the Politics of Culture: The Philippine Experience, Tuklas Sining, and the 10-volume CCP Encyclopedia of Philippine Art. For his publications, he has received five National Book Awards from the Manila Critics Circle and two Surian ng Wikang Pambansa awards.