The National Library of Thailand (Thai: หอสมุดแห่งชาติ) is the legal deposit and copyright library for Thailand. It was created in 1905, after the merger of the three pre-existing royal libraries. It operates under the jurisdiction of the Fine Arts Department of the Ministry of Culture and is located in Bangkok.
The library aims to be a fully high-tech national intellectual property heritage resource, serving all people and guided by professional library leadership.
More information on the Wikipedia page 
The website, in Thai is