Board Gender Diversity, Critical Mass, and Firm Performance: Evidence from Thailand

This study examines whether the share and number of women on corporate boards are associated with the financial performance of Thai listed firms. Using a hand-collected 2012–2021 panel of 584 firms listed on the Stock Exchange of Thailand, excluding financial institutions (5475 firm-year observations), we estimate models with firm and year fixed effects, with Tobin’s Q and return on assets (ROA) as performance measures. Critical mass is examined with three classifications from the literature: Kanter’s typology, a 30% threshold, and the number of female directors. With firm and year fixed effects, neither the share of women nor any critical mass category is significantly associated with Tobin’s Q. The ROA estimates are negative but imprecise, and they disappear when the pandemic years 2020 and 2021 are excluded. Confidence intervals rule out large effects in either direction. Models with firm fixed effects alone show significant negative associations, but these reflect common trends: Female representation rose during the period while the performance of Thai listed firms declined. The study adds evidence from an emerging market without a gender quota and with widespread family control, and it shows that omitting time effects can make common trends appear as an effect of board composition.