The objectives of the study were: 1) To study the level of creative thinking of the secondary school students in Thailand. (2) To study the factors affecting the level of creative thinking of the secondary school students in Thailand, that is, taking care of guardians, the environment of students, the classroom interaction of teachers and students, and the socio-economic status. (3) To study the relationship between the creative thinking and academic achievement of secondary school students. 

The hypothesis of the study were: (1) The level of creative thinking of students in secondary schools of Thailand is in medium level. (2) There is no significant difference between mean scores of creative thinking of students in secondary schools belonging to different groups of the taking care of guardians. (3) There is no significant difference between mean scores of creative thinking of students in secondary schools belonging to different groups of the environment of students. (4) There is no significant difference between mean scores of creative thinking of students in secondary schools belonging to different groups of the classroom interaction between teachers and students. (5) There is no significant difference between mean scores of creative thinking of students in secondary schools belonging to different groups of the socio-economic status of students. (6) There is no significant relationship between the creative thinking and the academic achievement of secondary school students of Thailand. 

The researcher followed the process of Multi-Stage Stratified Sampling. The sample comprised of 569 secondary school students.

The tools used were: The Students Personal Information Blank, the Scale to Inquire About the Environment of Students, and the Test to Measure the Creative Thinking of Students. 

The present researcher decided to adopt survey as well as testing and non-testing (rating scale) techniques which were the most appropriate methods of obtaining specific information. 

The analysis of variance, correlation, and t-test were used to analyze the data. 

The findings of the study were: (1) The analysis of the level of the creative thinking and the factors affecting on the level of creative thinking of secondary school students: (1a) The creative thinking of secondary school students was in medium level. (1b) The creative thinking (fluency, originality, and elaboration) were in medium level whereas the creative thinking (flexibility) was in high level. (1c) The taking care of guardians, the environment of students (technology, social, mass-media, pollution), the classroom interaction (the characteristics of teachers, the interaction of teachers and students, the encouragement about learning behavior of students, the acceptance of students’ ideas), the socio-economic status (level of education of guardians, monthly income of guardians, occupation of guardians, number of members in family) affected the level of creative thinking of secondary school students whereas the environment of students (culture) did not affect the creative thinking of secondary school students. (2) There is high relationship between the creative thinking and the academic achievement of secondary school students. (3) The environment around the students either technology, social, mass-media and pollution affected the level of creative thinking of secondary school students, it was found that the students belonging to the environment of high technology group were in high level of creative thinking. It was further seen that the modern technology has a part in helping the students to initiate in new things more increasingly. (4) The technology was the factor affecting the level of creative thinking in total and in different components, that is, fluency, flexibility, and elaboration. (5) The social was the factor affecting the level of creative thinking in total and in different components, that is, fluency, flexibility, and elaboration. (6) The culture was not the factor affecting the level of creative thinking in total but it was the factor affecting the level of creative thinking in different components, that is, fluency, originality, and elaboration. (7) The pollution  affected the level of creative thinking. (8) The classroom interaction between teachers and students has to play an important role in the creative thinking skills of secondary school students either the characteristics of teachers, the interaction behavior of teachers and students, the encouragement about learning behavior of students or the acceptance of students. (9) The socio-economic status of students, i.e., the education of guardians, monthly income of guardians, occupation of guardians and number of members of family also affected the creative thinking of secondary school students. (10) There was high relationship between the creative thinking and the academic achievement of secondary school students.