BA in the humanities - doing MA in Computer Science? I have a BA degree in sociology, but during my studies I got interested in programming and development. I would like to continue and do my MA thesis in a Computer Science University, and maybe, try to incorporate sociology and CS in my final thesis.

If I do it the other way around, going to sociology MA but try to get some computer science subjects along the way, I don't think will teach me much.

I would like to know if it's possible to continue and do a Masters thesis in CS, having already finished a BA in social sciences / humanities?
Yes, it is. The process of enrolling in grad-school is two-fold. First, the grad-school department (as an academic and administrative unit) verifies whether or not you're eligible to enroll as a graduate student (e.g., sufficient GRE scores, TOEFL scores - in case of international students, etc.). Second, the academic unit (CS in your case) verifies that the candidate grad-student is eligible to enroll in their program. Either you have a sufficiently robust CS background (e.g., you were a double major or at least you have a minor in CS) or you are willing to take fundamental CS undergrad classes (e.g., Data-Structures &amp; Algorithms, Operating Systems, Theory of Computation, etc.). These options minimize the risk of floundering with relatively complex class-contents when you enroll in higher-level CS grad courses independent of your bachelor-degree background.

P.S.: According to my experience, usually you're awarded a M.S. (M.Sc.) degree when you finish a C.S. masters program. Are you planning on taking humanities-based courses as part of graduate courses (this is the only way I know you would be awarded an M.A. instead of an M.S. for C.S.)?