Polyethylene terephthalate (PET) is today a largely used material in a broad window of industrial sectors, such as microelectronics, food processing, and medical devices.  The possibility of processing and modify PET substrates with micrometric resolution and limited thermal effects makes pulsed lasers the optimal tools for high precision applications. In this work, selective ablation of PET substrates is carried out by a UV ns source (BLOOM lasers) with average power up to 60 W and maximum repetition rate up to 4 MHz. The source allows to control the pulse duration from 2 ns to 20 ns and to work in burst regime of up to 5 pulse-per-burst depending on the selected pulse duration. Thanks to an efficient fiber MOPA architecture, BLOOM laser sources offer excellent beam qualities (M²<1.1, 5% astigmatism, 99% circularity) up to 4 MHz with short pulse duration (down to 2 ns) together with 15 kW peak power, making them an affordable alternative to Q-Switch lasers for PET ablation, with better quality, higher throughput and better temporal management of the process. Here, a parametric study is presented to evaluate the best achievable resolution for ablation of PET with limited thermal effects. For this purpose, the minimal pulse duration was employed (2 ns) while the material modification was controlled by varying the average laser power and by tailoring the light absorption by burst-mode irradiation.