the Germans (well not all Germans, but the high command, including dim shitted willy) ABSOLUTLY DID NOT WANT more Asian holdings. this was partially due to concerns of overextension, but a great deal of racism helped too
Do you have any citations for this? It's a pretty strong claim, and usually countries
do have an interest in acquiring additional territory.
The Germans seemed perfectly happy to take vast swathes of sub-Saharan Africa, most of which were the poorest parts of France's empire. Indochina, on the other hand, brought in greater revenues than the Brazilian central government, and due to French policies concerning self-sufficiency the colony also bore no outstanding expenses. Indochina possessed a great deal more strategic value than Sub-Saharan Africa too, being a potential springboard to better secure what was at the time the world's largest growth market; Chinese investment and commerce. While French Indochina lacked navally significant ports, it could likely provide colonial troops and supplies in a way Tsingtao never could. Most French troops deployed for policing in China were
sourced from Annam, and significant numbers of Indochinese served on the Western Front.
Also remember that British and Portuguese African possessions were unavailable to Germany in 1919, leaving only French and Belgian colonies. As the former were relatively unprofitable, the latter was running at a loss, and they'd no longer be putting resources toward occupying Anglo-Portuguese colonies, it makes sense to me that the Germans would look elsewhere to compensate.
Naval overextension is of course a legitimate concern, but Germany presumably possessed an equal or greater ability to project power compared to France even before the war, given its larger navy. Japan wasn't an overriding concern in 1919, with its second/third rate navy, and the non-participation of the United States in the war, plus the absence of the Lansing-Ishii Agreement, means Germany could likely count on the United States as a balancing power- a role it had played in East Asia since (at the very least) 1900. With France cut out of the region entirely, the only power able to seize German East Asian colonies unchallenged would be Britain; a second major naval contest with which would threaten German African holdings just as much as Indochina, making them no more viable.
At the end of the day it's also worth remembering that if Indochina became too problematic Germany could always attempt to sell or exchange the colony. Wilson wasn't waving his 14 points in everyone's faces KRTL, so self-determination and decolonization wouldn't be at the forefront of anyone's minds.
As for the matter of racism, I'm not sure I understand the argument there at all. Europeans were, on the whole, about as racist toward East Asians as Africans at the time, so I'm not sure why ruling over one would be more or less acceptable than the other on a purely racial basis. Maybe I'm misunderstanding the intended angle, though.
For French economic claims, see this
linked document.
For naval size comparisons, see
P. G. Halpern's "A Naval History of World War I".