Please suggest disertation topic related to international business?

I think replication studies are very useful. Pick a major topic that is being discussed in global research, and then try to use the same method in your own country to see whether the global trends are really global. For example, one very hot paper at the moment (Crucini, Mario J., M. Ayhan Kose, and Christopher Otrok. "What are the driving forces of international business cycles?." Review of Economic Dynamics 14.1 (2011): 156-175.) would be very interesting to test with businesses in one country that are trying to internationalise. This is another good option: Forrester, William R., and Manfred F. Maute. "The impact of relationship satisfaction on attributions, emotions, and behaviors following service failure." Journal of Applied Business Research (JABR) 17.1 (2013).

I think either of these would make easy dissertations which would make a real, if small, contribution to academic studies.

Also take a look at Hennart, Jean-François, and Arjen HL Slangen. "Yes, we really do need more entry mode studies! A commentary on Shaver." Journal of International Business Studies 46.1 (2014): 114-122.