Pseudoxytenanthera stocksii (Munro) T.Q.Nguyen, Bot. Zhurn. (Moscow & Leningrad) 76: 993 1991. (syn: Dendrocalamus stocksii (Munro) M.Kumar, Remesh & Unnikrishna; Gigantochloa stocksii (Munro) T.Q.Nguyen; Oxytenanthera stocksii Munro; Pseudotenanthera stocksii (Munro) R.B.Majumdar);
India; Vietnam as per Catalogue of Life
Shrubs; stems glabrous or softly pubescent, slender, grey-green, solid; nodes with a softly pubescent ring. Leaves 10-20 x 1.2-2 cm, shortly petioled, tip setaceous, base rounded or cuneate, beneath glabrous or hairy, midrib narrow; nerves 5-6; sheath striate; ligule rather long, toothed. Spikelets 1 cm long, in globose heads spinescent, glabrous, fertile and sterile; empty glumes 2, ovate, mucronate, 5-7 nerved; flower glumes 2 ovate, subacute, dorsally mucronate. Anthers short, acute. Ovary ovoid, hairy; style long, slender; stigma 1, simple, plumose. Grain elongate, beaked, smooth.
Banks of rivers
(Attributions- Dr. N Sasidharan (Dr. B P Pal Fellow), Kerala Forest Research Institute, Peechi as per India Biodiversity Portal)
Maybe Gigantochloa apus
OK but for the record I did not find any thorns or flowers
Dendrocalmus strictus it is I think
Please see this link. looks quite close also mentioned as distribution in northern Western Ghats.
though I am not 100% sure
I think there picture is not clear and we have to rely on more reliable sources.
References: POWO Catalogue of Life The Plant List Ver.1.1 WCSP IPNI India Biodiversity Portal
Dendrocalamus stocksii (Munro.): A Potential Multipurpose Bamboo Species for Peninsular India– Edition: 2013- Publisher: Institute of Wood Science and Technology (Indian Council for Forestry Research & Education) Bangalore
Green Gold Manga Bamboo (Dendrocalamus stocksii) for Commandable Profit from Cultivable Wasteland