In Phnom Penh I always use the PassApp for any vehicle, anywhere.
I.e. maybe I am at the end of one of those entertainment streets and lots of TukTuks demand outrageous prices.
Open PassApp, select the vehicle type, point on a map where you want to go and a minute later one of those TukTuks from the corner will come and drive like with a meter. No hassle, just great service.
Someone should introduce that service in Thailand. Everybody would love it - except the scammers.