There have been multiple attempts to bring in subtrees from other nations to Japan with the most contentious being South Korea. I disapprove of adding South Korea as just a subtree of another nation however as both Koreas can stand on their own and have a fairly developed Military-Industrial Complex that can churn out indigenous designs of their own and for them to be only a subtree would mean that the various oddities that both nations have will never shine its light.
Thailand on the other hand had been a historical ally of Japan during WW2. There is precedence for them to be merged in a single tech tree and I dont see how anybody would disapprove of adding Thailand as a subtree for Japan. Thailand also has some interesting vehicles to offer and can fill some gaps here and there that is crucially missing for the Japanese tech tree. There is a caveat however, as although Thailand can fill those gaps, I have decided to why not add in the rest of the Greater East Asia Co-Prosperity Sphere into the mix however I only limited it to maritime SEA as Vietnam (which would probably include the rest of Indochina as well - Laos & Cambodia) is already part of the Chinese tech tree. While I do understand that most of the countries part of the GEACPS were puppets and were never truly independent, as well as these countries do not collaborate that much with the JSDF on weapons development & procurement - Japan for the most part has maintained quite the large influence over maritime SEA especially through the Asian Development Bank & JICA and the numerous bilateral treaties Japan has with maritime SEA. Essentially, Japan is still considered a big player within SEA with many looking up to Japan for training and expertise. Gameplay wise, it makes Japan an interesting nation to play as it is the penultimate amalagamation of weapons development designed for the conditions of the Pacific.
I would like to extend huge thanks to the work done by NiceNiti and Nikolai_Kachorn's proposal on the forums on which I base most of the additions here. Pikpikker's ASEAN tech tree proposal has also been of great help. u/HyperGull's expanded tech tree proposal has also been very beneficial. I am not gonna lie, I only copy pasted whatever they have added but I just picked and chose the best vehicles to add into the tech tree because my goal here is to just expand the Japanese tech tree and not overwhelm it. However if someone has to be credited, its the work of these people who should receive it. I have tried to remain as faithful to use Thailand more though as Thailand was Japan's nominally independent ally so I didnt add much vehicles that are in the arsenal or maritime SEA and added them as premiums instead. This is mostly to add more premiums into the Japanese tech tree as well.
