Should i reduce milk in the recipe if I live in high humid weather like Singapore: 35c and humidity as high as 90%?pore

You could, but I would recommend simply using a bit more flour in the first stage of kneading the dough. The tangzhong is a carefully balanced mixture, and the cold milk used in the next step is going to be needed to cool it down sufficiently so as not to kill the yeast when it is added in. The instant yeast also needs enough liquid to rehydrate. When baking, it's not unusual to need to adjust the flour amount anyway, to allow for variance in humidity and such. You won't likely need as much extra flour as you think, and it won't hurt anything.