What is the fine-grained topic of the following text: Ou Virak, a Cambodian-American economist who heads Future Forum, a research institute based in Phnom Penh, said Kem Sokha’s imprisonment had served its purpose and that the release was expected, given Hun Sen’s longtime habit of imprisoning his rivals and critics before elections and freeing them afterward. Only return the topic.
Release of Kem Sokha after imprisonment in Cambodia