The ultimate barrier from forming a single party to replace the coalition certainly is the Bumiputera (son of the soil or generally Malays) special rights which being strongly upheld by UMNO even after strong opposition by the non-Bumiputeras (mainly Chinese and Indian).
The ultimate barrier from forming a single party to replace the coalition are the Bumiputera (son of the soil or ethnic Muslim Malays). Ethnic Malays, who by law must be Muslim, are endowed with special privileges in accordance with Islamic Sharia Laws which are strongly defended by UMNO despite opposition by the non-Bumiputeras (mainly Chinese and Indian).