The Belt and Road Initiative (BRI) is a series of strategic infrastructure investments that aim to intensify economic cooperation and support long-term development. The China-Laos Railway, connecting Kunming (China) with Vientiane (Laos), is one of the key railway projects in the Southeast Asian region, aimed at improving transport accessibility and boosting economic growth. The aim of this study was to determine the impact of this investment on the economic convergence of regions along the railway route, with particular emphasis on changes in trade flows, investment dynamics, and access to international markets. The study is based on econometric methods and statistical analysis, which allow for a quantitative assessment of the impact of the railway on economic development and the convergence process. Particular emphasis is placed on aspects related to sustainable growth, including the even distribution of economic benefits, the impact of investment on labor markets, and potential risks resulting from Laos’ debt and economic dependence on China. Data comes from official economic statistics and reports of international financial institutions. The results of the analysis allow for a better understanding of the mechanisms of regional development in the context of large infrastructure investments and their compliance with the concept of sustainable and inclusive economic growth. The conclusions can be a reference point for future investment strategies and policies supporting long-term economic development in developing countries.