Epstein-Barr virus (EBV) infects over 90% of the global population and establishes lifelong persistence. Although early childhood infections are often asymptomatic, EBV infection during adolescence can cause infectious mononucleosis, several malignancies, and posttransplant lymphoproliferative disorders. The timing of EBV infection and seroprevalence varies globally based on geographic and socioeconomic factors; however, comprehensive and updated data for Thailand are limited. This study investigated EBV seroprevalence across age groups in four provinces representing Thailand's regions, comparing findings with previous data and exploring correlations with economic and health care indicators. Serum samples (N = 1,274) were collected between May and August 2024 from participants ages 6 months old to 80 years old in Ayutthaya, Uttaradit, Buri Ram, and Trang provinces. EBV capsid antigen IgG levels were measured using ELISA. Age-specific seroprevalence increased from 35.9% in infants (6 months old to 2 years old) to nearly 100% in adolescents and adults, with varying antibody levels between age groups. Comparisons with historical data illustrated consistent trends of early EBV acquisition in childhood, but the infection increased slightly slower than in the past. Compared with other countries, EBV seroprevalence in Thailand and other developing countries occurred earlier than in developed countries. Linear regression analysis revealed a significant correlation between age at 50% and 75% EBV seropositive and a national economic indicator (gross domestic product per capita). These findings found little changes in EBV epidemiology over time and provided updated information and analysis to support public health strategies.