This ambanja was sold to me as a male. I have started getting doubts, and now I think it is female. I want to get a few more opinions before I call the breeder.
I agree that it is a male, but not because of a bulge. Your cham is too young to be showing a bulge (At least not that I could see). That being said the shape of the tail just behind the vent is indicative of it being a male.
I agree. the area just posterior to the vent looks like there is a spot for a hemiphenes to develop into. Female tails are a bit thinner at the base around the vent than in males.