The purpose of this study is to examine the relationship between board composition and sustainability disclosures of firms listed on The Market for Alternative Investment, Thailand. The 209 observations of firms listed on The Market for Alternative Investment during 2018-2019 data are collected from annual reports, 56-1 forms, and firms' financial statements. Using multiple regression analysis, this study finds that the chairman independence is positively associated to firms' sustainability disclosures. Moreover, firms' CG which is control variable in this study is positively associated to firms' sustainability disclosures. In addition, firms' industry which is another one of control variable is also associated to firms' sustainability disclosures. These results imply that board independence is positively associated with firms' sustainability disclosures of firms listed on The Market for Alternative Investment, Thailand.