Abstract
Background: COVID-19 pandemic has affected humanity in several aspects of life. Not only create health problems, but also economic and social problems. To cope with this pandemic, we need to know and understand how to have the COVID-19 preventive behavior. Hence, this study will be focusing on factors that influence people to have COVID-19 preventive behavior.

Objectives: The aim of this study is to assess knowledge, attitude, and COVID-19 preventive behavior of high school students.

Materials and Methods: The study was conducted using a questionnaire. A total of 325 students participated. Knowledge, attitude without presence of rules, and attitude with presence of rules toward COVID-19 preventive behavior were assessed. Independent t-test and analysis of variance were used to analyze differences between outcomes and socio-demographic. COVID-19 preventive behavior was analyzed by a generalized linear model.

Results: Students revealed a good level of COVID-19 related knowledge, correctly answering 4.48 (standard deviation [SD] = 0.70) questions in a total of 5, good levels of attitude both without and with the presence of rules, average score was 11.05 (SD = 1.16) of four questions and 15.86 (SD = 2.07) of six questions, respectively, and a good level of COVID-19 preventive behavior, the average scores at 44.28 (SD = 6.68), in a total of 11 questions.

Conclusion: This study revealed a good level of knowledge, attitude both without and with the presence of rules and COVID-19 preventive behavior among high school students at Loei Pittayakom School, Thailand. Mainly, the factor that may influence them to get a high score in all four sections is staying active with news and the latest information presented on the internet. In addition, the study demonstrated that there was a relationship between attitude with the presence of rules and COVID-19 preventive behavior. Therefore, having regulations can lead to having preventive behavior.

Key words: COVID-19; Preventive Behavior; High School Students