The sole way to achieve that would be for France to transfer (parts of) Indochina (France controled Cambodia, Cochinchina and a few treaty ports in Tonkin and Annam) to Germany following the Franco-Prussian War instead of Alsace-Lorraine, which IIRC was proposed IOTL. Now if Wilhelm I reluctantly accepts (Bismarck would probably have accepted that in order to maintain good relations with France, which he originally wanted, and to appease those guys screaming for annexations), then... You'd have Germany doing a similiarly bad job in the region just like France did IOTL. Though maybe they wouldn't expand THAT much, resulting in an independent Empire of Vietnam (maybe allied with Germany and a rival of Siam and China).
They could use that as a way to "jump" to the Philippines though, which could be appealing to Germany if they were more prominent in (South) East Asia. German rule wouldn't be kind to the Filipinos though.