They definitely care for the motorcycle endorsement in Chiang Mai. I would like to add that you can get a Thai license on a tourist visa. I did this since I didn't have a motorcycle endorsement.
In my experiences, the police in Chiang Mai don't make a distinction between scooter or motorcycle. If it's on two wheels and has a motor, you need a motorcycle license. Either an international one (with motorcycle stamp) or a Thai motorcycle license.
I live in Chiang Mai and I can tell you for certain your international license is fine for a scooter/motorbike only if you have a motorcycle classification in it from back home. Otherwise, you will need to get a Thai license and pass a vision test, written test, driving test, medical test, etc.
There's a dude that works "off the books" and can get the residency certificate done in one day in Promenada for a 500 thb "fee." I've done it twice now (drivers license and bank account). Although I'm hearing here's on vacation. Bottom floor by the parking lot, close to immigration, right next to the copy place in an empty commercial space. It's not an agency. It's literally a one dude who sits in an empty space. You can't call him or email him. You simply walk in and hand him the documents. He looks at them, then asks for money. After you pay him, he says "tomorrow after 2pm" and then you walk out. No receipt, no small talk. The next day you walk in, he hands you cert, and you walk out. No smiles, all business.