This is an interesting question but perhaps not for the reason that you might think. Many historians have tried to understand why Japan was the only major non-European country to fully industrialize and transform into an imperial power. Of course, they certainly weren't the only ones to give it a go. Qing China, Persia, and the Ottomans all undertook efforts to industrialize/"modernize" in different ways. Geography is a key consideration here. Japan was a relatively small country (as compared to the Qing) and had relatively lower costs of governance. Furthermore, it was isolated which gave it breathing room and the opportunity to avoid European/American intervention, unlike Siam or Persia. While Siam was able to maintain its autonomy its influence was curtailed by both French and British interest to its east and west respectively. That being said, king Mongkut did in fact pursue some successful modernization efforts, particularly in the legal field. However, this did lead to an attempted coup after his death when his young son, Chulalongkorn, took the throne and attempted similar efforts. Because of this, modernization efforts slowed down substantially. Because of these reforms state power became more centralized which contributed substantially to efforts to avoid European domination (much like Japan).

Industrializing was also influenced by geography. Some industrialization projects were undertaken in Mongkut's reign. But ultimately most efforts were focused on state centralization, something that Japan had achieved long before the Europeans began their push into East Asia. Furthermore, the distribution of natural resources hindered industrial efforts. The Japanese government was able to maintain strict control over natural resources through powerful conglomerates (zaibatsu) and there were significant iron, coal, and oil deposits within Japan. Siam did not have the luxury of a centralized state or strategic natural resources.