Rasbora elegans looses the stripe to a great extent with age leaving just the spots.
Another "half striped" Rasbora is R. somphongsi which is a rounder fish and tends to have a brighter line above the dark half line. This species rarely grows above 25mm and is very shy.
A remote possibility is R. vulgaris, a most inappropriate name, (vulgaris means common), because this is a rare fish. It is similar in appearance to elegans, but has just the half line, not the spots.
I'll also add R. einthovenii to the list of possibles. It does have a complete stripe, which extends through the caudal fin, (tail), BUT, it used to be called Rasbora vegae - and looking at the title of the thread...