This question already has an answer here:
The R&D startup my friend is working for is acquired by a big US tech giant after a long joint venture. She is coming from the 2nd world country, where the company is based too. She and her colleagues are working on the integration of the products with the American counterparts. They are basically doing the same work, for the same company (now), only at different locations. Yet they are still paid the same 2nd world salaries, which is like 5-10x smaller. I don't think it is fair, but she was told she won't get a raise, let alone to the same levels.
What is the best course of action to take to actually get some reward for the years of hard work? Said company is proudly an equal opportunity employer, but I doubt federal laws have effect overseas.