The only way I stay cool is just to remind myself it's not my country, and I repeat this mantra as many times as needed. I think next time I will do what I've often done in the past, just park the tuk-tuk on the side of the garage, bring a bagged lunch, and pay the mechanic for a half day of access to his tools 😄. This is actually really common here, often the customer can use the mechanic's tools better than the mechanic, only in Cambodia.
It's just a general lack of education and also not wanting to get educated. Even in specialty clothing stores, my wife will ask if something is 100% cotton, the seller says yep, then I look at the tag to see it's polyester and nylon. I find it all too common that people can run a business and spend zero time getting acquainted with their products or services. Converting frustration to laughter is something I am still not zen enough to do yet, but perhaps in my 40s this will manifest in my personality 🤦♂️.