(1) Background: Violence against each other via social media has increased and caused cyberbullying that can happen anytime through electronic communication tools that everyone can access easily. So, this study aims to investigate causal factors contributing to youth cyberbullying in Thailand's three Southern border provinces. (2) Methods: The subject group consisted of 340 youths and the data were analyzed with structural equation modeling (SEM). (3) Results: The study found that the model of the causal factors resulting in youth cyberbullying in the three Southern border provinces was consistent with the empirical data (the relative chi-square (χ2/df) was 1.77. The goodness-of-fit index (GFI) was 0.95. The root-mean-square-error of approximate (RMSEA) was 0.049). Cyberbullying was positively influenced directly and indirectly by negative upbringing, the influence of personal violence, and the influence of media violence at a statistically significant level of 0.001, with total effect sizes of 1.13, 0.74, and 0.64, respectively. Additionally, cyberbullying was positively influenced directly by negative mental traits with a statistically significant level of 0.05 and a total effect size of 0.17. (4) Conclusions: The study results could be beneficial in concretely forming policies and strategies to prevent and mitigate the problem of youth cyberbullying.