It is apparently Impatiens from section Oppositifoliae. It could be I. chinensis, but I don't see shape of stem - in I. chinensis it should be quadrangular.

As the specimen comes from southern India, best to ask ...

---

Putting here a cropped version of one of the above photos to get closer to stem, which looks to me, more terete than quadrangular ...

Also adding another two cropped pictures from above posted photos to get closer to the flowers (though from different plants in same place).

---

If the spur is puberulous, it could be Impatiens brevicornis (Barnes) Bhaskar stat.nov. (= I. chinensis var. brevicornis Barnes). Pls see my publication on 'Taxonomic monograph on Impatiens L. (Balsaminaceae) of Western Ghats - p.124. 2012.

---

The posted photos do not show the relevant aspects for ID to species level.

I will label them as Impatiens sp.

---

Family: Balsaminaceae

(Description as given in https://indiabiodiversity.org/species/show/281300)

Annual herbs, about 15-30 cm tall. Stems erect, woody, terete, succulent, long, glabrous or shortly sparsely hairs. Leaves opposite decussate, linear lanceolate-elliptic to linear oblong, about 2-10 x 0.3-1.4 cm across, base subcordate, acute or rounded, margins finely serrate with prominent teeth, basal serratures often setaceous, apex acuminate, lateral veins about 4-7 on either side of the midrib, green sparsely scabrid hairy above and paler glaucous and veins brownish, beneath, petiole sessile in lower leaves and subsessile above, stipules subulate, recurved, with persistent stipular glands. Inflorescence resupinate, axillary, solitary or fascicled in the upper parts of the plant, usually glabrous. Flowers bisexual, zygomorphic, white, rose purple, or pale scarlet, about 1.8 cm across, pedicel slender, variable, ascending, about 2-3 cm long, deflexed in fruit, sepals 3, imbricate, 2 lateral ones flat, small, linear, acute, usually green, glabrous, about 5-7 mm long, posterior sepal (Lip) large, petaloid, obovate, bucciniform or boat shaped with some marking on one side, spurred, spur abruptly constricted, incurved bow like, inflated in middle and hook-like or bifid, minutely hirtellous, about 1-1.8 cm long, petals 5, free, purple, pink, white or reddish voilet, upper standard petal, keeled or cucullate, orbicular-obcordate, bilobed, apex shortly acute, about 5-7 x 4-8 mm across, lateral ones (wings or alae), fused in pairs, basal lobes ovate-triangular to elliptic, about 4 mm long, distal lobes, broadly elliptic, about 2-2.2 cm long, curved upwards, dorsal auricle absent. Stamens 5, alternating with petals, anthers bi-locular, pollen 4 colpate. Ovary 5 locular, superior. Fruit indehiscent, capsule, narrow fusiform or elliptic, about 1.2-2 cm long, swollen in the middle, loculicidally dehiscing by 5 valves, springing away elastically from axis, glabrous. Seeds many, globose or oblong, black, shining, glabrous),