POD is in 1905. Russia does much better for some reason and the Japanese are locked out of Korea. Japan decides to take a risk and grab Korea while the Russians and French are fighting the Germans, with Britain on the sidelines. Then when Italy and Britain come in against the Germans, the war spreads to Indonesia and Malaya from Vietnam.
Perhaps a POD in 1898, where the Spanish bug out of Cuba and the US does not invade the Phillipines?
Only Britain and America of the colonial powers were really a threat to Japan. If Britain is not backing France and America is not in the Phillipines, what is going to stop Japan?
So if Britain is neutral at first, the Japanese are all over...
Russia in Korea, the Kuriles, Kamchatka, and Manchuria.
Spain in the Phillipines and Micronesia.
France in Vietnam.
Netherlands in Indonesia.
Then later it's time for...
Britain in Malaysia, Sarawak and Sabah, Brunei, and Hong Kong.
Portugal in Timor and Macau.