The correct answer is D) Singapore.
The Southeast Asian country that has a wealthy economy and a low unemployment rate and is ruled by a constitutional monarchy is Singapore.
Indeed, Singapore is one of the most important economies in this region of Southeast Asia. It has a high-income economy with a more than decent way of living for their citizens.
After Singapore got its independence, businessmen created a kind of powerful industry that impulsed the economy that contrasted with the poverty and low income that existed previous independence.