The research aims to study the factors affecting on volume and audit quality of Thai auditor by using empirical research. The population and sample in the research are the CPAs in Bangkok. The research tool are questionnaire with completed response totaling 157 units constituting 21.48% of response rate. The results show that factor that has positive affect with volume of auditing is type of audit office (t = 8.340***) and control variable is experience in auditing task (t = 3.399***) at significant level (α) < 0.001 ; whilst the factors that have negative affect with audit quality are competitive condition in auditing market (t = -2.420*) and volume of auditing tasks (t = -2.227*) at significant level (α) < 0.05. And the characteristics of auditors has a positive effect on audit quality (t = 11.964***) at significant level (α) < 0.001