Hey,Diploma holder has a very good value in the area of Construction. To be frank they are valued better than engineer. I would say work for 2 years and try if you can complete engineering as a correspondent course I.e if you want to be on the execution side. If no complete engineering right after diploma join courses like Advance construction management, Quantity surveying or any other management courses.Further you can also go for NDA or Autocad or even Bsc.

Hope,this information helpful for you.Goodluck.