A giant of a man named Barney, who stands out not only because of his size but also his childlike innocence, finds himself in Thailand. After being drugged and robbed, he is left with no money or passport, essentially stranded in a foreign land. Fortuitously, he crosses paths with two nice but fierce Muay Thai fighting sisters, Katen and Katoon, who offer him food and shelter. The sisters are soon impressed by Barney's unexpected combat abilities, which he discovers upon facing a local gang that harasses them. Recognizing his potential, the sisters invite Barney to train with them in Muay Thai, hoping that his giant stature and newfound skills can help them compete in a local fighting tournament and win the prize money.

As Barney becomes more adept in Muay Thai, he attracts the attention of various unsavory characters, including those looking to exploit his fighting talent for their own gain. The story balances action with the comedic elements of Barney's struggles to adjust to a culture and discipline that are entirely new to him. Throughout his training and the developing bond with Katen and Katoon, Barney learns about honor, friendship, and self-discovery, all while navigating the dangers that come with the world of underground fighting. This journey sets the stage for a showdown that tests Barney's limits and the strength of his new relationships.