Thailand successfully invades FIC, Sept 1940

I want to consider the possibility of Thailand successfully invading FIC in Sept-Dec 1940. This would be an earlier and more successful campaign for Thailand than in OTL https://en.wikipedia.org/wiki/Franco-Thai_War If by January 1941, Thailand has occupied all or most of FIC, how do Britain, Japan, DEI, USA, Vichy France, Germany, etc. react?

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After being called out for starting new threads instead of adding to existing ones on similar topics, I thought I'd undertake an indepth search.

Feb 2014 - Deutschland, Thailand , and a real Pacific Axis
https://www.alternatehistory.com/discussion/showthread.php?t=308033

May 2010 - Kingdom of Greater Thailand timelines
https://www.alternatehistory.com/discussion/showthread.php?t=155998

Feb 2009 - Thailand 'Wins' WWII!
https://www.alternatehistory.com/discussion/showthread.php?t=115192

Sep 2007 - Thailand pulls a Japan
https://www.alternatehistory.com/discussion/showthread.php?t=70578&highlight=thailand
 
Not much difference from OTL. The Japanese would mediate the peace and both Thailand and Indochina gets sucked into the Japanese sphere. I don't think it matters much to the Japanese if Thais got more land as long as they're subordinate to them.
 
posted that earlier thread that Germany could have cultivated Thailand as trading partner similar to or instead of KMT China.

added benefit would be they have revanchist goals against France too.

once Vichy French regime established, Axis could dictate territorial adjustments as during Second Vienna Awards.
 
If it's an outright invasion, they probably get counted as an enemy power by the US, leading to occupation post-war.
 
If it's an outright invasion, they probably get counted as an enemy power by the US, leading to occupation post-war.
FIC was not really the US' sphere of interest at the time. Thailand invading the territories of defeated France before the Japanese make their move is hardly going to lead to US occupation post war. If the US is going to invade and occupy Thailand, they're presumably also taking FIC. That's make the 1950-1970 rebellions against foreign occupation and war in SEA more interesting.
 
Do they really have to invade, Thailand has no good options late on?
In 1945 all they have to do is demand occupation right and Thailand will have to say yes or face everybody not agreeing to a surrender and Thailand cant possibly fight even a token effort from GB or FR without any allies.
 
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