Background: This paper examines the efforts of consultants affiliated with Philip Morris (PM), the world's leading transnational tobacco corporation, to influence scientific research and training in Thailand via the Chulabhorn Research Institute (CRI). A leading Southeast Asian institute for environmental health science, the CRI is headed by Professor Dr. Her Royal Highness Princess Chulabhorn, the daughter of the King of Thailand, and it has assumed international significance via its designation as a World Health Organization (WHO) Collaborating Centre in December 2005. Methods and Findings: This paper analyses previously confidential tobacco industry documents that were made publicly available following litigation in the United States. PM documents reveal that ostensibly independent overseas scientists, now identified as industry consultants, were able to gain access to the Thai scientific community. Most significantly, PM scientist Roger Walk has established close connections with the CRI. Documents indicate that Walk was able to use such links to influence the study and teaching of environmental toxicology in the institute and to develop relations with key officials and local scientists so as to advance the interests of PM within Thailand and across Asia. While sensitivities surrounding royal patronage of the CRI make public criticism extremely difficult, indications of ongoing involvement by tobacco industry consultants suggest the need for detailed scrutiny of such relationships. Conclusions: The establishment of close links with the CRI advances industry strategies to influence scientific research and debate around tobacco and health, particularly regarding secondhand smoke, to link with academic institutions, and to build relationships with national elites. Such strategies assume particular significance in the national and regional contexts presented here amid the globalisation of the tobacco pandemic. From an international perspective, particular concern is raised by the CRI's recently awarded status as a WHO Collaborating Centre. Since the network of WHO Collaborating Centres rests on the principle of "using national institutions for international purposes," the documents presented below suggest that more rigorous safeguards are required to ensure that such use advances public health goals rather than the objectives of transnational corporations.