Abstract Background Governance processes play an important role in shaping the formulation and implementation of policy measures such as restrictions on marketing of ultra-processed foods. However, there is limited analysis of the factors that affect governance for nutrition, especially in low- and middle-income countries such as Thailand and the Southeast Asia region. This study aimed to examine governance factors that create opportunities and challenges for the introduction of policy to restrict food marketing in Thailand, in line with the WHO recommendations to restrict food marketing to children. Methods A qualitative study design was used. Interviews were conducted with 20 actors with experience and in depth knowledge of food marketing in Thailand, including government, civil society, industry and international organisations. Open questions were asked about experiences and perceptions of the governance processes related to policies for restricting food marketing in Thailand. Themes were derived from the 3-i Framework which relates to interests, ideas and institutions influencing the introduction of food marketing policy were identified and analysed using abductive methods. Results Actors viewed institutional challenges as a significant barrier to advancing effective regulation of food marketing. Three major clusters emerged from the data: interests (priorities, relationships), institutions (formal structures, informal structures, broader institutional strategies), and ideas (norms). The study has three major findings in relation to these factors, highlighting the influence of formal structures, institutional interests in food marketing issues, and ideas in promoting multisectoralism. The siloed nature of policymaking was reflected in the government failing to stimulate engagement among key actors, posing challenges for implementation of effective policy change. Contested interests led to disagreements between actors over food marketing agenda and thus competing policy priorities. Consistent with these findings, the lack of effective mechanisms to promote multisectoral coordination across diverse actors reinforced barriers to policy change. Conclusion The findings highlight ongoing challenges to the government’s aim to strengthen policy to restrict food marketing which, without greater coordination in governance mechanisms, will hinder effective regulation and the achievement of public health goals. This analysis suggests that the Government should prioritise the development of a holistic, multisectoral approach to improve governance for better nutrition outcomes by overcoming policy silos.