A rapid expansion of trade liberalization in Thailand during the 1990s raised a critical question for policy transparency from various stakeholders. Particular attention was paid to a bilateral trade negotiation between Thailand and USA concerned with the impact of the 'Trade-Related Aspects of Intellectual Rights (TRIPS) plus' provisions on access to medicines. Other trade liberalization effects on health were also concerning health actors. In response, a number of interagency committees were established to engage with trade negotiations. In this respect, Thailand is often cited as a positive example of a country that has proactively sought, and achieved, trade and health policy coherence. This article investigates this relationship in more depth and suggests lessons for wider study and application of global health diplomacy (GHD). This study involved semi-structured interviews with 20 people involved in trade-related health negotiations, together with observation of 9 meetings concerning trade-related health issues. Capacity to engage with trade negotiations appears to have been developed by health actors through several stages; starting from the Individual (I) understanding of trade effects on health, through Nodes (N) that establish the mechanisms to enhance health interests, Networks (N) to advocate for health within these negotiations, and an Enabling environment (E) to retain health officials and further strengthen their capacities to deal with trade-related health issues. This INNE model seems to have worked well in Thailand. However, other contextual factors are also significant. This article suggests that, in building capacity in GHD, it is essential to educate both health and non-health actors on global health issues and to use a combination of formal and informal mechanisms to participate in GHD. And in developing sustainable capacity in GHD, it requires long term commitment and strong leadership from both health and non-health sectors.