hello mani,

yes,you can do b.tech after diploma.as a diploma holder you're having 2 choices

1.you can start your b.tech engineering from direct second year-lateral entry

2.otherwise you can start from a scratch(first year)-as a fresher

the lateral or fresher entry is depend on the institution in which you wanna take admission.some may conduct separate university entrance exam or some colleges will give based on the merit or state/central entrance exam for lateral entry.so all depends on the institution.

all the best!

I Hope this information will be useful to you.

if you need additional information,let us know to help you.

Thank you!!!:)