This Japanese website has a good reference collection of Rapalas, showing male/female & upper/undersides.

Plate 1 : R. varuna, manea, scintilla, duma, iarbus & rhodopis
Plate 2 : R. rhoda, hades, domitia, pheretima, suffusa & dieneces
Plate 3 : R. damona, caerulescens, ribbei, dioetas, enipeus & cassidyi
Plate 4 : R. diopites, masara, arbaimuni, cowani, nissa, elcia & rhoecus
Plate 5 : R. melida, zamona & tomokoae

Note, however, that most of the shots are of Philippines subspecies, which may have some differences from the SouthEast Asian ones. But I believe that some of the species are recent discoveries which are new to science.

Just because C&P4 and Fleming do not list some of these species doesn't mean they can't appear here in Singapore. So do look out carefully for them, although ID'ing from field shots would prove a bit challenging for these lookalikes - some of which look so similar that it would have us .