The fluctuations of the measured phase operators in the thermal squeezed states are calculated with the aid of thermo field dynamics. Two kinds of fundamental quantum mechanical fluctuation are introduced, one is associated with two quadrature components of measured phase, an other is associated with one quadrature component of measured phase and photon number. From these, we investigate two kinds of squeezing of fluctuations for measured phase in thermal squeezed states and their relations to temperature.