Is it possible to become a research assistant just after b.tech? I am a recent bachelor of technology graduate from India and want to become a research assistant just after b.tech at any abroad university (USA,CANADA,UK, etc). If it is possible then what kind of qualifications, GPA, academics are required? Also for becoming an RA at these universities is the GRE exam necessary?
Yes.

First be admitted to graduate school.

Then convince a professor to hire you.