Interesting question.

This is a very interesting one. It contains comments on 'other' post-colonial theories.

Chen, K.-H. (2010). Asia as method : toward deimperialization. Durham NC: Duke University Press.

I also wrote some. Check here at RG.

Best wishes

Not sure, the question is what you would like to study. 

I agree that the answer depends on the kind of study you are undertaking. But if you are not already familiar with him, I can recommend the work of James W. Scott.

I would like to focus on this topic from international relations point of view. The only theory which comes to my mind is Can subaltern speak? by Gayatri Chakravorty Spivak 

Neo-colonialism might be deemed a more appropriate term than the postcolonial if the minorities are still struggling for rights. There are works on other comparable countries (eg. the Mainland Chinese in Hong Kong and the Irish in Britain being singled out for discriminatory treatment in the absence of no visible differences in colour). Check out the special issue on Hong Kong - Mainland China tensions in Inter-Asia Cultural Studies 2015, 16 (3).

http://www.tandfonline.com/toc/riac20/16/3#.VmfcIYTldSU

I second the motion on James C. Scott's Domination and the Arts of Resistance, and I'm thinking you might benefit from my essay "Conjuring Crypto-Jews in New Mexico" in Boundaries, Identity and Belonging in Modern Judaism, eds., Diemling and Ray, Routledge (2015).  It examines agenda-driven, academic adventurism in redefining the ethnic and genomic identity of a minority population without training in the requisite disciplines, and it touches on the consequences of  neo-colonialism in the region. 

Contrary to some suggested thoughts here, the Chinese in Vietnam are no longer, since the so-called liberalization of the market in the late 1980s, an oppressed minority but instead "control 50 percent of the city's market activity", as Wiki states, "and have achieved economic prominence in the light industry, import-export, shopping malls, and private banking causing much resentment with the indigenous Vietnamese."

They are certainly not a "subaltern" minority, as that term is understood by postcolonial theory. Subaltern stands for groups that are "outside of the hegemonic power structure of the colony and of the colonial homeland." While it is true that the Chinese, or, as they are known, the Hoa people, are sometimes the subject of reprisals by the majority Vietnamese, they are a very powerful economic group, similar, though not to the same extent, to the position of Jews in America. 

Postcolonial theory, therefore, will be of no use to your question. 

As far as I know, the powerful position of Chinese in Vietnamese economy was caused partly by French different taxation policies applied on Chinese and Annamese in Indochina and Cochinchina, in which the Chinese had more privileges. Therefore, as a target of communism, capitalists incl. rich Chinese were already in danger in the North Vietnam during the land reform in the 1950s and in the South during "cải tạo tư sản" (Capitalist Reform) after 1975. The deportation of Chinese and Hoa Kiều out of Vietnam around 1979 was the result of political conflict between Vietnam and China (related to Cambodian issue) among the relations of socialist countries (Vietnam with China and Soviet Union). This powerful position of Chinese in Vietnamese economy has been recreated after đổi mới (1986) by the very intimacy relation between the two communist parties of China and Vietnam especially after the disappearance of Soviet Union in 1991. In these historical and socio-political contexts, I think, theory of post-communist transformations could be suitable for you.

I think consepts like Diaspora and hybridity can help you. Generally, post colonial theories give you good idea to analysis your subject or problem.

Taking an international perspective, the common, contemporary term, for a permanent populace of Chinese descent outside the PRC is "overseas Chinese". In the literature, one would come across the "Chinese diaspora". Diaspora as a process and the resulting conflicts in identity are interesting focal points.

Article The Overseas Chinese in the Socialist Republic of Vietnam, 1979-82

Article Comparative Diaspora Politics: The Cases of China and India

Article A comparative analysis of diaspora policies

Article Hybrid diaspora and identity-laundering: a study of the retu...

Article Homecoming or tourism? Diaspora tourism experience of second...