This trail follows little used narrow four wheel drive roads and walking tracks. There are some ruts, some rocky sections, some sandy patches, a few quite steep slopes and occasional mud but overall it's easy going. It's nearly all down hill, through tropical forest, past a coffee plantation, with frequent views over the Chiang Mai valley. There are no signs - you need a guide.
Mountain biking is popular with adventurous tourists in this hilly area of northern Thailand. The infrastructure is well established with commercial operators offering shuttles, bike rental and guides - complete packages. It's very organized, reasonably priced and hassle free. Lunch is normally provided. The rides go daily - you'll join other people wanting to do the same ride. There are at least half a dozen trails with varying degrees of difficulty. The Eagles Route described here is one of the easier ones. To find your shuttle and guide just google "Chiang Mai mountain biking".