The thermal remagnetization (TR) of permanent magnets, that is the irreversible increase of the magnetization due to temperature increase after dc-demagnetization at the starting temperature T-0, is especially large for well aligned sintered SmCo5 pen-nanent magnets. The TR is strongly correlated with the temperature coefficient of the coercivity, with the coercivity mechanism and variations of internal local fields by magnetostatic interaction. We present experimental results regarding the influence of the initial temperature T-0 on the TR for a commercial SmCo5 sintered magnet with a high demagnetization factor N. This dependence on T-0 is interpreted theoretically by taking into account the demagnetization factors of the grains n, and of the sample N respectively. We found, that the TR-maximum increases with decreasing T-0, and that its position shifts slightly to lower temperatures, what is in agreement with the results of the model calculations.