Singapore is already a regional power, but what if the British hadn't dissolved the Straits Settlements, and what if, instead of only Singapore doing it, the entirety of the former colony (Singapore, Malacca, Dinding, Penang, Christmas Island, the Cocos Islands and Labuan) had declared its independence from Malaysia, or had been elevated to the status of Commonwealth realm like in As One Star Sets, Another Rises? All the constituent parts of the colony were either multiethnic or had a Chinese majority/plurality, after all, instead of being solidly Malay.
The result would've been a Singapore multiplied by four and with access to a sizeable amount of oil and gas. A Commonwealth/Republic of the Straits could've become obscenely rich and powerful. If Sarawak had maintained its sovereignty and North Borneo had become a sovereign state under the ruling dynasty of the Sultanate of Sulu, they'd probably be better off than the current Malaysian provinces, too - they wouldn't be as rich as the aforementioned wanked Singapore, but they could've been able to pull a South Korea and enter the First World in a matter of only a few decades.
Today, Brunei, Sabah, Sarawak and the Straits would be the South East Asian (and much nicer) version of the states of the Persian Gulf.