I think you mean the Hòa Hảo sect, unless those photos are meant to depict female warriors fighting in the service of a popular brand of instant noodles.
As for their anti-northern stance well it’s a bit more complicated than that. At the time those photos were taken the Hòa Hảo were in an alliance with the Viet Minh against the French. That broke down and they did become fierce opponents of the communists. Their military had essentially been disbanded or absorbed into SVN government forces by the time it became a North-South civil war.
If you have ever read Graham Greene’s ‘The Quiet American’ you’ll recognise the Hòa Hảo as the ‘third force’ touted by Pyle, the earnest but fatally naive and eponymous American of the title.