The slow evaporation approach has been successfully utilized to produce a single crystal of benzothiazolium amine salicylate (BTAS) with methanol as a solvent. The compound’s monoclinic crystallization with space groups P21/c and Z = 4 was demonstrated by SCXRD. The synthesised BTAS crystal's functional groups were discovered through the use of FTIR and Raman spectroscopic analysis. Analysis of UV–Vis absorption and transmittance confirms that BTAS possesses outstanding transparency in both the near-infrared (NIR) spectrum as well as visible spectrum. The crystal exhibits a lower cut-off wavelength, indicating minimal absorption in these spectral ranges. The photoluminescence (PL) spectra of BTAS crystal exhibit a blue light emission centered at 408 nm. Exhibiting exceptional 3rd order NLO characteristics (Non Linear Optical), the BTAS crystal possesses (χ3) of 1.72 × 10⁻4 esu, n2 of 8.542 × 10⁻4 m/W, and β of 3.479 × 10⁻12 cm/W. This demonstrates the resultant crystal's potential for cutting-edge optical applications.