Place: Assam
Habit: shrub

… the colours of flower are very deep compared to the those found in Desmodium heterocarpon; general appearance of the inflorescence is almost ditto.

YES, my first choice was also D. heterocarpon, but the colour of the flower is different. Moreover, the shape of the leaves is also lanceolate not elliptic or broadly obovate, like in D heterocarpon

Photos are not clear..but I doubt it to be a Polygala sp.

The inflorescences look similar to Desmodium heterocarpon…..