This paper aimed to study if student self-assessment reports improved the mathematics teaching and learning experiences of students in Nakhon Phanom province, in Upper Northeast Thailand. The qualitative research module used focused on the effectiveness of student self-assessment (SSA) in teaching remotely during the COVID-19 pandemic in a Thailand junior high classroom with 37 mathematics students. The qualitative research conducted an evaluation study involving one class using self-assessment. Data were collected from student self-assessment (SSA) records, interviews and a questionnaire. SSA records were collected at the end of every lesson. The questionnaire was given at the end of the topic. Focus group interviews were conducted using a small number of open questions. The analysis similarities and differences, and an expert group were involved to lessen the chance of researcher bias. Findings revealed that student self-assessment reports improved the junior high students' experiences of mathematics teaching and learning in the following ways: (1) improved their communication with the teacher; (2) improved students' understanding of what they needed to learn; (3) improved students' confidence to ask for help from the teacher; (4) provided further evidence of students' progress and problems; (5) improved students' self-directed learning. In the culture of Thailand, students respect teachers and adults. This has the effect of making students afraid to ask questions in class and to not dare to think differently from the teacher's instruction. Therefore, student self-assessment reports while promoting mathematics learning for students, also helped students improve their confidence to communicate with their mathematics teachers and in self-directed learning. Furthermore, it enhanced students' understanding of learning and could possibly be used to solve learning problems. The implications of the findings go beyond the specific context of the COVID-19 pandemic and provide directions for other teachers and researchers.