We studied temperature-dependent amplified spontaneous emission (ASE) in CsPbBr₃ perovskite thin films. For temperatures 180-360 K, a narrow-band lasing is observed. However, a new accompanying ASE band appears below 180 K, indicating a more complicated behavior. The two ASE bands are strongly correlated and in competition; they are assigned as exciton and bi-exciton recombination. We estimated the exciton binding energy (E_B = 27.3 meV) and that of the bi-exciton, which is lower than the E_B. The reduced effective mass of the exciton is estimated as μ = 0.11 m_e. This discovery identifies more details of the ASE phenomenon.