Excellent news from the Far East, things progress apace. Siam always struck me as fairly opportunist, so shouldn't be any problem there, I can easily see the leadership changing sides in the face of the Empire's advance. The French colonies however could go either way.
If they think it's just a return to French rule, then is the Japanese alternative really any worse? Probably not, unless things have gotten really rough under Japanese management.
Now if Britain says the area will get self-government ala the rest of the Empire that is a nice carrot and an improvement over Japanese (and indeed pre-war French) rule. But I doubt France will be all that pleased with losing Indochina and is setting of a massive rift with Paris worth the benefits in the East? I'd say yes, but British governments of all colours are prone to regrettable outburst of Francophilia so they may try and keep Paris happy.