A surface plasmon resonance (SPR) based optical touch sensor structure is proposed that provides high switch sensitivity and requires weak activating force. Our proposed SPR-based optical touch sensor is arranged in a compact Kretschmann-Raether configuration in which the prism acting as our sensor head is coated with a metal nanofilm. Our optical-based noise rejection scheme relies on wavelength filtering, spatial filtering, and high reflectivity of the metal nanofilm whereas our electrical-based noise reduction is obtained by means of electrical signal filtering process. In our experiment proof of concept, a visible laser diode at 655 nm centered wavelength and a prism made from BK7 with a 50-nm thick gold layer on the touching surface are used, showing a high measured 7.85 dB optical contrast ratio for the first touch. An estimated weak mechanical force of < 0.1 Newtons is also observed for sufficiently activating the desired electrical load. It is tested for 51 operations without sensor malfunction under the typical and very high illuminations of 342 lux and 3000 lux, respectively. In this case, a measured average optical contrast of 0.80 dB is obtained with a +0.47 dB fluctuation, implying that the refractive index change in a small 3.2% of the overall active area is enough for our SPR-based optical touch sensor to function properly. Increasing optical contrast in our SPR-based optical touch sensor can be accomplished by using a higher polarization-extinction-ratio and narrower-bandwidth optical beam. A nice controlled environment and gold coated surface using thin film sputtering technique can help improve reliability and durability of our SPR-based optical touch sensor. Other key features include ease of implementation, prevention of light beam becoming incident on the user, and ability to accept both strong and weak activating forces. /A surface plasmon resonance (SPR) based optical touch sensor structure is proposed that provides high switch sensitivity and requires weak activating force. Our proposed SPR-based optical touch sensor is arranged in a compact Kretschmann-Raether configuration in which the prism acting as our sensor head is coated with a metal nanofilm. Our optical-based noise rejection scheme relies on wavelength filtering, spatial filtering, and high reflectivity of the metal nanofilm whereas our electrical-based noise reduction is obtained by means of electrical signal filtering process. In our experiment proof of concept, a visible laser diode at 655 nm centered wavelength and a prism made from BK7 with a 50-nm thick gold layer on the touching surface are used, showing a high measured 7.85 dB optical contrast ratio for the first touch. An estimated weak mechanical force of < 0.1 Newtons is also observed for sufficiently activating the desired electrical load. It is tested for 51 operations without sensor malfunction under the typical and very high illuminations of 342 lux and 3000 lux, respectively. In this case, a measured average optical contrast of 0.80 dB is obtained with a +0.47 dB fluctuation, implying that the refractive index change in a small 3.2% of the overall active area is enough for our SPR-based optical touch sensor to function properly. Increasing optical contrast in our SPR-based optical touch sensor can be accomplished by using a higher polarization-extinction-ratio and narrower-bandwidth optical beam. A nice controlled environment and gold coated surface using thin film sputtering technique can help improve reliability and durability of our SPR-based optical touch sensor. Other key features include ease of implementation, prevention of light beam becoming incident on the user, and ability to accept both strong and weak activating forces.