I did my 90 day at the new office today. For me it's now a 62km round trip instead of a 7km one.
It's easy to find because of the large water tower at the side of it. You can see it from some distance away. But you have to go nearly 3km past the site to get to the next U-turn if you're coming from Khon Kaen up Mittrapharp.
They have a separate office for 90 day reporting. It's on the 1st floor (2nd floor if you're American) and outside the office is a lady with a photocopier who checks your documents and copies any missing ones. But I had mine already done. In the office you hand your paperwork and passport to a man sitting behind a counter, he checks it and hands it to another person to fill in the receipt with the new date and staple it in your passport. When ready she calls your name, you collect your passport and off you go. Do be careful exiting the car park as you drop down a steep ramp onto Mittrapharp.
There does appear to be a lift (elevator if you're American) but I needed the exercise.