The five-member censorship panel said the Thai-produced film could "persuade viewers to falsely believe" incorrect information, and was a threat to national security and international relations.
The film, Fah Tam Pan Din Soong, or Boundary, was directed by Nontawat Numbenchapol. It recounts the journey of a private who took part in the 2010 crackdown on the red shirts before returning home to Si Sa Ket.
The film then shifts to a discussion about border spats between Thailand and Cambodia, featuring several interviews with residents on both sides.
The film also includes YouTube footage of Thai soldiers in action during a border skirmish in 2011, a survey of damage from Cambodian shellings, and a long monologue from a Cambodian soldier who criticises Thailand.
The film, shot over two years with support from the Asian Cinema Fund in South Korea, ends with peaceful images of the Preah Vihear temple.
"I made the film because I wanted to look at issues confronting our society, from the red-shirt and yellow-shirt problems to the Preah Vihear issue," Nontawat said.
But the censorship committee, which is attached to the Ministry of Culture, objected to many "groundless" points in the film.
One concern is a caption explaining that there were "nearly 100 deaths" during the red-shirt crackdown at Ratchaprasong on May 2010. The official figure is 89.
The panel was also concerned by comments made by the Cambodian soldier when he discussed border demarcation.
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