Who said that a Chinese, Indian or any other can’t be a Prime Minister of Malaysia? What’s to stop him? Here’s the Constitution: Article 43 – Appointment of the Prime Minister and the cabinet[edit]
The Yang di-Pertuan Agong is required to appoint a Cabinet to advise him in the exercise of his executive functions. He appoints the Cabinet in the following manner:

acting in his discretion (see Art. 40(2)(a)), he first appoints as Prime Minister a member of the Dewan Rakyat who in his judgment is likely to command the confidence of the majority of the Dewan. There is no Constitutional requirement that the Prime Minister must be of any particular race or religion;[17] and
on the advice of the Prime Minister, the Yang di-Pertuan Agong appoints other Ministers from among the members of either House of Parliament.

Lest I forget, from the list of Malaysian Prime Ministers . . . from Tunku Abdul Rahman to Najib, who can you claim to be legally or biologically a “PURE MALAY”? From Siamese blood to Bugis & Indian, you can see a stream of foreign blood in their heritage!