This study investigates the relationship between information flow and corporate governance of Thai listed company during 2000-2007. The study uses corporate governance indices which capture major aspects of corporate governance that are board structure, conflict of interest, board responsibility, shareholder rights, and disclosure and transparency. The measurement of private information flow will use firm-specific return variation and Probability of information based trading (PIN) as alternatives of information flow. The results show that corporate governance is negatively related with private information flow. Strong corporate governance reduces private information flow relative to the public information. The better corporate governance will alleviate information based trading and reduce informational asymmetries. Moreover, this study indicates that board structure, conflict of interest , board responsibility are the sub-indices of corporate governance that have a negative relationship with private information flow while the rest sub-indices are not influence with information flow.