The temperature dependence of transmission spectra near the two-phonon states zone of TlGaSe2 crystals is investigated. The additional band at 142 K and a decrease of transmission at 257 K are observed. It is shown that the successive thermocycling processes between the commensurate and incommensurate phases lead to appreciable changes in these spectra. The experimental results are explained by revealing of phase transitions at indicated temperatures, the influence of semiconductor properties and layer disordering of the TlGaSe2 crystal.