The selection was made by a committee of 22 members from Thailand 's Federation of National Film Association, including president Chaiwat Taveewongsangthong.
The lavish historical epic is directed by Prince Chatrichalerm Yukol as the second installment of a trilogy about the life of 16th century warrior King Naresuan.
The picture was released back-to-back with the first film in February. With each over two hours long, both became smash hits with a combined box office of more than $14.6m (500m baht).
While the first part focuses on the childhood of the prince who would later become the warrior king, the second part has a more dramatic story revolving around how the prince set the Siamese free from the control of the Burmese.
The last film is currently in production and will likely be released only next year.
Prince Chatrichalerm is best known for 2003's historical epic Suriyothai which was re-cut by his film-school friend Francis Ford Coppola for the international audience.