Species within the genus Eurema range from Asia, Africa, Australia, and Oceania, to the Americas. 
At least 71 species are currently known. 
There are 9 species within the genus Eurema in in Vietnam; Eurema brigitta, laeta, hecabe, blanda, andersoni, ada, simulatrix, novapallida and sari.
The main differences between the species are:
a) the number of spots in the underside forewing cell, combined with
b) the shape of the upperside forewing black markings and
c) the shape of the apical area markings on the forewing underside. 

Eurema hecabe (sometimes also called Common Grass Yellow) ooks very similar to the Eurema blanda (sometimes also called Three-spot Grass Yellow).
The difference, however, is on the underside of the forewing.
In Eurema blanda there are three small spots and a fourth bigger one in the middle; in Eurema hecabe there are two small spots and one bigger spot in the middle.
Eurema hecabe probably rivals Eurema blanda for the title as the most common Grass Yellow in Vietnam. 
They both are found in urban locations as well as forested areas.

1st photo: Cuc Phuong National Park, Ninh Binh, Vietnam, 12 January 2024
Last 4 photos: My Son Sanctuary, Hoi An area, Vietnam, 30 December 2023