Sunset at Chaopraya is based on the novel Khu Kam wrote by Thommayanti. It tells the love story between a young Thai woman and a Japanese officer during World War II.
Angsumalin is the daughter of a high ranking Thai official who lives with her mother and granddaughter, on the banks of the Chao Phraya river, in Thonburi (Her father is now married to another woman).
When Thailand signs a cease fire agreement with Japan, Japanese soldiers start arriving in Thailand. Their goal is to use Thailand’s railways and infrastructures to invade neighboring countries, including Burma. Kobori, a Japanese officer in charge of engineering matters, falls for Angsumalin at first sight. It is not the case for Angsumalin. She dislikes Kobori for being Japanese therefore an invader and also because of a promise she made to Vanut.
Vanut, Angsumalin’s closest friend, left for England to study. Having feelings for Angsumalin, he asks her to wait for him (So selfish). Angsumalin is now stuck with this stupid promise.
Kobori, who isn’t fazed by Angsumalin’s behavior toward him, pursues her – visiting her house, being nice to her family, etc. Little by little Angsumalin finds herself drawn to him. Yet, her pride (That pride SMH) causes her to push Kobori away.
An unfortunate (Fortunate for us viewers :-D) event has Kobori and Angsumalin in a comprimising situation that leads to their hasty marriage. During an attack by Western forces, Kobori protects Angsumalin by laying on top of her. They are later found in that position by several villagers. In order to protect Angsumalin’s name, the two have no choice but to get married. Angsumalin’s father had also been pushing for the union between her daughter and Kobori to create stronger ties between Japan and Thailand.