Controlling shareholders in listed firms can impact accounting quality. When they have power, they align with minority shareholders for better disclosure. But when they lack power, they may prefer lower quality to hide true performance. The study looked at firms in the Stock Exchange of Thailand from 2008-2012. Different accruals models were used to measure accounting quality. Results show that when controlling shareholders have enough power, accounting quality is high (alignment effect). But when they lack power, accounting quality may be lower (entrenchment effect).