I love that deep red!!!
To tell the difference the main thing to tell is if it has long fins or not. ( Male-long fins, females-short ) There is also a Plakat Betta, which have short fins whether it is a male or not. Females have an egg spot as well. I think there is a sticky or thread somewhere that shows the differences... Hope that helped.
defiantley a male he is very pretty
females will have a white dot, between there ventrals (on the belly) males have it when there young. another way to tell (more accurate) is that black area under there gills that is called there "beard", males have it larger when they flare, and it sticks out without even flaring still, awhile females goes under the gills, only shown when they flare
most of the time females have short fins MOST of the time, not all