Nano-crystalline tin (II) oxide (SnO2) was successfully synthesized by a simple and cost-effective surfactant assisted solution precipitation technique. The structural, optical, and morphological characterization of as synthesized nano-crystalline SnO2 was confirmed by X-Ray diffraction (XRD), ultraviolet-visible (UV-Vis) spectroscopy, and transmission electron microscopy (TEM). The nano-crystalline SnO2 possesses tetragonal lattice structure (rutile phase) with preferential growth along (101) plane and average crystallite size of 8 ±2 nm were confirmed by XRD Rietveld refinement. The TEM images were showed quasi spherical particles with average particle size of 10 ±2 nm. The optical energy band gap of 3.76 eV confirms the electronic conduction mechanism in SnO2. Furthermore, the synthesized nano-crystalline SnO2 with 15 wt % glass frit was used as a functional material to fabricate thick film sensors using cost-effective screen printing method.  The sensor shows high sensitivity towards H2, CO, and LPG selectively at optimal operating temperatures of 120, 150 and 70 o C respectively for 100 ppm concentration of each gas. The improvement in sensitivity, selectivity, and stability at low operating temperature and their correlation with the nano-crystalline SnO2 (101) plane, small particle size and optical band gap were also envisaged along with repeatability, reproducibility, calibration, and aging effect.