The objective of this research is to develop glass materials using rubber wood ashes from biomass power plants in Yala Province. From the analysis of the chemical composition of rubber wood ash from the biomass power plant in Yala Province. It was found that the amount of CaO was the main component. The researcher then designed a glass formula that uses rubber wood ash from biomass power plants in Yala Province as part of the glass structure formula. It consists of SiO₂, B₂O₃, Na₂O, CaO and ZnO according to the following ratios: 45B₂O₃: 5SiO₂: 20Na₂O: (25-x)CaO: 5ZnO percentage by weight. By adding rubber wood ash at x = 0, 5, 10, 15, 20 and 25 percent by weight. Then melt the glass in an electric furnace at 1200 °C for 3 h. After that, the molten glass was poured into a stainless-steel mold using the normal melt-quenching technique and annealed at 500 °C for 3 hours and then allowed to cool to room temperature. The density and the refractive index of the glass samples tended to decrease with increasing amount of rubber wood ash. In terms of absorbance analysis in the wavelength range 400 – 2,000 nm, it was found that the absorbance peak at wavelengths around 460 and 1,052 nm was caused by changing the energy level from ⁶A_1g (S)  ⁴T_2g (G) and ⁵E(D)  ⁵T₂(D), respectively.