We demonstrate all-optical magnetic switching (AOS) in an amorphous Tb30Fe70 thin film, triggered by a 5.1 MHz laser oscillator. The magnetic layer is grown on SiO2/Si substrate. An identical magnetic film deposited on a microscope glass slide reveals no AOS but solely thermally induced demagnetization. This effect is due to heat accumulation by multiple laser pulses because of the low thermal conductivity of the glass substrate. In contrast, the use of a proper heat sink (e.g. SiO2/Si) avoids the need for low repetitive laser amplifier systems to induce AOS and paves the way for a cheap and simple technical implementation using conventional laser oscillators.