marking and making trails

For marking a well-preserved trail, a GPS unit aligned with an appropriate base-map is the modern way of doing it. Might need to read up on GIS limitations, especially in jungles. Also mark significant waypoints like major road intersections, river crossings, and other features that will not change in the immediate future. It goes without saying to become very familiar with land navigation (both electronic and map/compass). Maybe a modern GIS class or even certificate, … it would definitely help but there's some programming involved.

As to making new trail, you may need to take into account government, tribal, and private boundaries, as there may be a land owner or land manager who needs to give permission. Not sure if you can get those electronically, … might need to consult some old atlases or maps.

Would there already be trails that the indiginous local people use for travel, commerce and trade? They have lots of trails for that in the Nepalese Himalaya.

Make sure whatever you do is not going to land you in prison. I have not heard good things about Myanmar prison.