Brunei is around the same size as Trinidad and Tobago.

Trinidad and Tobago is approximately 5,128 sq km, while Brunei is approximately 5,765 sq km, making Brunei 12% larger than Trinidad and Tobago. Meanwhile, the population of Trinidad and Tobago is ~1.4 million people (927,592 fewer people live in Brunei).
Tip: This to-scale comparison of Trinidad and Tobago vs. Brunei uses the Mercator projection, which distorts the size of regions near the poles.