This study investigates the entanglement and squeezing characteristics of light generated by a non-degenerate, coherently driven three-level laser in an open cavity, coupled to a thermal reservoir through a single-port mirror. By solving the master equation and Hamiltonian, we derived the steady-state solutions for the atomic operators, enabling us to calculate the average photon number, quadrature variance, entanglement, and normalized second-order correlation of the cavity radiation. Our results indicate that higher spontaneous emission rates significantly reduce the average photon number, while the mean of thermal light ($\langle n_{th} \rangle$) enhance it. We found that the light is squeezed primarily in the minus quadrature, achieving maximum squeezing of 37.9% at $\langle n_{th} \rangle = 0$, and slightly decreasing with increased thermal effects. Spontaneous emission reduces photon number variance, while thermal reservoirs amplify it. Additionally, squeezing enhances entanglement, and both are interdependent, with higher squeezing producing more entanglement. These results have implications for quantum communication, computing, and sensing by improving secure communication, error correction, and measurement precision.