10. Prince Albert II, Monaco
Net worth: $1 billion
Prince Albert II of Monaco's net worth reportedly comprises a fourth of the land he reigns over; the Philadelphia-area home of his mother, Grace Kelly, which he purchased in 2016 for an estimated $754,000; an antique car collection; shares in a Monte Carlo resort; and a pricey stamp collection.
9. Emir Sheikh Tamim bin Hamad Al Thani, Qatar
Net worth: $1.2 billion
Emir Sheikh Tamim bin Hamad Al Thani took over the throne of Qatar after his father, Hamad bin Khalifa Al Thani, stepped down in 2013.
The former emir's estimated net worth of $2.4 billion comes from Qatar Investment Authority, which manages the country's oil and gas reserves.
8. Grand Duke Henri, Luxembourg
Net worth: $4 billion
The Grand Ducal Family of Luxembourg doesn't receive a salary, but has been granted around $324,851 every year since 1948 to carry out functions. Not that they need it, since their net worth is in the billions.
7. Emir Sheikh Mohammed bin Rashid al Maktoum, Dubai, UAE
Net worth: $4.5 billion
Vice President, Prime Minister of the United Arab Emirates, and Emir Sheikh of Dubai, Mohammed bin Rashid al Maktoum, has spent some of his wealth on charitable donations, such as $10 billion to create the Mohammed bin Rashid Al Maktoum Foundation, which focuses on helping future generations develop sustainable solutions.
6. Prince Hans Adam II, Liechtenstein
Net worth: $5 billion
The Princely House of Liechtenstein's fortune is largely due to its privately owned bank, LGT Group, and investments made through the Prince of Liechtenstein Foundation, which oversees real estate, forest, and winery assets.
5. King Mohammed VI, Morocco
Net worth: $5.7 billion
King Mohammed VI's wealth largely comes from his family's ownership of SNI, a private holding company that invests in other African countries and operates in banking, telecommunication, and renewable energy.
4. Emir Khalifa bin Zayed Al Nahyan, Abu Dhabi, UAE
Net worth: $15 billion
The President of the United Arab Emirates and Emir of Abu Dhabi, Khalifa bin Zayed al Nahyan has amassed a fortune as chairman of the Abu Dhabi Investment Authority, which manages the UAE's excess oil reserves.
3. King Salman bin Abdulaziz Al Saud, Saudi Arabia
Net worth: $17 billion
The source of King Salman bin Abdulaziz Al Saud's wealth comes from his family's ownership of a media group, including pan-Arab daily Asharq Al-Awsat and Al Eqtisadiah.
2. Sultan Hassanal Bolkiah, Brunei
Net worth: $20 billion
The Sultan of Brunei profits well from the oil and gas industry — he lives in the world's largest palace, which costs more than $350 million, and reportedly owns more than 600 Rolls-Royce cars.
1. King Maha Vajiralongkorn, Thailand
Net worth: $30 billion
King Maha Vajiralongkorn and his family made their money off of investments derived from the Bureau of the Crown Property, which manages the property of the crown of the Kingdom of Thailand.
He owns the 545-carat Golden Jubilee Diamond, the world's largest cut and faceted diamond.
