Love of Siam shows the relationship between a weak family, a lonely girl, and teenagers who start to know the meaning of love and friendship that will remain in their memory forever. The story begins when old friends Tong and Mew meet by chance at Siam, a well-known place where teenagers in Bangkok hang out. Tong is a popular and handsome boy who is bored with his pretty girlfriend like Donut. Tong just discovers that a pretty girlfriend is not the answer to something in his life. While Mew is a quiet guy, who is obsessed with music and secretly loved by Ying, a girl next door. Mew is facing a hard time trying to compose love songs after his grandma dies. Later, Mew introduces Tong to June, a girl who looks alike Tong's lost sister. Tong comes up with a plan for his mother to hire June to be his sister, hoping to cure his father of alcoholism. June accepts the offer and becomes a part of Tong's family. Everything in Tong's family seems to have become better since June's arrival. June is loved by Tong's family, but she begins to question if what she is doing is right.