International research documents the popularity of youth e-cigarette use and factors associated with consumption. However, less research has examined the behaviour in jurisdictions where such products are illegal. This study therefore investigated social and demographic factors associated with the use of e-cigarettes among youth in Thailand, where such products are prohibited. An online cross-sectional survey was conducted among middle and high school students (n = 6,111) to capture individual, interpersonal, organizational, and social factors potentially related to the behaviour. Multinomial logistic regression was used to assess associations with e-cigarette susceptibility and use. The prevalence of e-cigarette susceptibility was 15.9%, with 9.7% reporting current use. Risk factors, including lower GPA, current smoking, current substance use, and peer vaping, were associated with susceptibility (vs. non-susceptibility) and use (vs. susceptibility). Parental vaping was linked solely to current use, while middle school attendance, current alcohol use, exposure to e-cigarette use in school and exposure to online marketing, were linked to susceptibility. Negative attitude towards e-cigarettes and regular exposure to anti-e-cigarette activities in school were protective factors against both. High-risk perceptions and regular parental supervision were protective factors for susceptibility. Despite bans, a significant proportion of Thai youth engage in e-cigarette use or are susceptible to it. Unique factors influence susceptibility and use, highlighting the need for strengthening laws and adjusting prevention efforts.