Helene is right: her pictures show two different forms (not species) of nagyi.
The first picture shows nagyi from around the location of Cherating. It is clearly recognizable by the fact that the coloured band in the caudal of the male is blue, or to say it in other words: the same colour as the coloured bands in dorsal and anal.
The second and the third pictures show a nagyi from around the location of Kuantan (which is more widely distributed), and it is clearly recognizable by the fact that the colour of the band in the caudal is white (whereas the bands in dorsal and anal are blue).
The Kuantan-form is the “classical” one, and is to be recognized in some other features, too. For instance: the caudal appears to be very short indeed because of the rather long overstanding spines. This is less the case in Cherating. But this feature is not clearly to be seen in these photos.
The first who caught this species was Peter Nagy de Felsö Gör from Salzburg, and Dietrich Schaller (Munich) described the species some years later using his name. It was the Kuantan-form. Only some years later Martin Hallmann (Weinheim) detected the Cherating-form and its aberrant features.
We don’t know whether these differences that are always clearly to be seen in live fish indicate subspecies or some less important difference only. In any case: One should not mingle those forms! Keep them separate!