This study aimed to examine the relationships between consumer motivation, trust, and the purchase decision-making process through social media platforms among consumers in Nakhon Si Thammarat Province. The sample consisted of 400 consumers who had prior experience purchasing products via social media, with data collected using an online questionnaire. The data were analyzed using descriptive statistics—frequency, percentage, mean, standard deviation—as well as t-tests and one-way ANOVA. The results revealed that most respondents were female, held education levels below a bachelor’s degree, worked in the private sector, and earned between 15,001 and 25,000 baht per month. TikTok emerged as the most frequently used platform for online purchases. The primary motivational factors influencing purchasing behavior were document management and novelty, while service quality and brand image were the most emphasized trust-related factors. Within the purchase decision-making process, problem recognition and evaluation of alternatives were rated as the most important stages. Hypothesis testing showed that demographic factors had no significant effect on purchase decisions. However, surveillance motivation was significantly related to information seeking and evaluation of alternatives, while escape motivation influenced post-purchase behavior. Additionally, brand image negatively affected problem recognition, whereas information seeking had a positive effect on purchase decisions. Based on these findings, it is recommended that marketers prioritize TikTok-based marketing strategies by enhancing consumer motivation and trust through a focus on quality and brand image, thereby stimulating purchasing decisions through social media channels.