The purposes of this research were (1) to forecast the export value of Thailand’s automotive and auto-parts industries in 2020 and (2) to assess the impact of Coronavirus 2019 (COVID-19) on Thailand’s automotive and auto-parts industries in 2020. The study employed a monthly time series of export value of Thailand’s automotive and auto-parts from January 2010 to December 2019, a total of 120 months. The econometric techniques applied the SARIMA(p,d,q)(P,D,Q)s model for assessing the monthly impact of COVID-19 in 2020 to compare the export value between the actual value and forecasted value. The empirical results indicated that (1) SARIMA(0,1,1)(0,1,1)12 was the most appropriate model for forecasting, and it provided the export value of Thailand’s automotive and auto-parts industries in 2020 equal to 808,089 million baht. (2) The COVID-19 situation affected the export value of Thailand’s automotive and auto-parts industries in 2020, which was an economic loss equal to 159,321 million baht.