Jira Maligool and Vanridee Pongsittisak, executives and veteran producers at GDH (previously GTH). Jira came up with the film's premise when he heard on the news that SAT scores were being cancelled in China due to a cheating scandal. The producers then invited Nattawut Poonpiriya to direct the film. Nattawut had previously directed the company's 2012 psychological thriller Countdown, and the producers believed his abilities would lend themselves to developing Bad Genius as a heist film. Nattawut was immediately intrigued, and agreed to direct the project, which was developed under the working title "2B Come Won" (a reference to the 2B pencils used to fill in test choices). Nattawut wrote the script together with Tanida Hantaweewatana and Vasudhorn Piyaromna, researching the format details of current standardised tests, as well as actual methods of exam cheating from the news. The script took about years to complete. The story was developed as a Hollywood-style heist/caper thriller, but the writers made efforts to ground it in a context that would still be relatable to a Thai audience. A major challenge, according to Nattawut, was telling the story of students taking exams—"perhaps the most boring activity on earth"—in a compelling manner. The film's secondary theme, that of the characters' contrasting social backgrounds, emerged during the writing process. Casting The film's main cast was relatively inexperienced—none of the four young main actors had had film roles in a major studio production prior to 2017. Lead actress Chutimon Chuengcharoensukying, a fashion model, made her film acting debut as Lynn. Chanon Santinatornkul played the role of Bank, and Pat and Grace were played by Teeradon Supapunpinyo and Eisaya Hosuwan, respectively. (Teeradon and Eisaya had past TV acting experience, and Chanon had appeared in a few indie films as well.) According to Nattawut, casting for the four main actors took a long time before arriving at the four final choices, who were virtually perfect fits for their roles. He was so impressed with their work that he allowed them considerable room for improvisation during filming. The chemistry underlying Lynn and Bank's relationship, for example, was unscripted, and part of Pat's sales pitch speech was ad-libbed by Teeradon. The only veteran actor in a major role was Thaneth Warakulnukroh, who played Lynn's father. Primarily a singer and songwriter, Thaneth had been absent from acting for over thirty years when Nattawut came across a magazine interview of him, and invited