This study aimed to explore factors perceived to affect the intention of premarital sexual behaviours among junior high school students in Muang District, Thailand. A stratified random sampling technique was employed to select three schools out of ten public junior high schools. A situation analysis was conducted following a focus group discussion and in-depth interview. The informants included six junior high school students, five parents, three teachers, two health professionals and two school administrators. A thematic analysis was employed for the data analysis. Results illustrated negative attitude, social media, the internet use, socio-environmental space, peer pressure, social belief, low self-efficacy, generation gap and sexual education were the factors perceived to affect the intention of sexual behaviours. An integrated implementation of a comprehensive sexual education was the way forward to increasing self-efficacy.