Do tuk tuk drivers understand Google Maps in English.

If you show them a map always zoom in to show major landmarks nearby rather than just the street name as they navigate primarily by visual landmarks rather than official street addresses.

However older drivers in rural areas might struggle to read a digital map. The absolute best strategy is to have the phone number of your guesthouse handy. You can simply call the host and hand the phone to the driver so they can explain the exact directions in Sinhala.