On the throne since the age of 18, this year he celebrates both his 50th birthday and 50 years since his country's independence from Britain.
Often dressed in traditional robes, the king retains widespread support in rural eSwatini despite his reputation for lavish spending on planes and palaces while 63 percent of his subjects live below the poverty line.
The country, landlocked between South Africa and Mozambique, suffers the highest HIV adult prevalence rate in the world at 27.2 percent.
The king demonstrated his untrammelled authority earlier this year when making a surprise announcement that Swaziland would officially change its name to eSwatini ("land of the Swazis").
'People are scared'
In addition to curbs on opposition parties, anti-government protests are also effectively banned.
Marches are planned this week by striking civil servants, teachers and nurses, but the government said it "expected" trade unions to halt the action.
In June, police used rubber bullets to break up a rare demonstration by 500 trade unionists protesting against alleged government theft from the national pension fund.
"People can't express their views freely, they are scared," Shireen Mukadam, a researcher at rights group Amnesty, told AFP.
"eSwatini is an extremely closed society. There is a pervasive culture of secrecy.
"People are used to submitting to the king. The constitution itself says that he has absolute power."
Donor nations have had little success in lobbying for greater freedoms.
The European Union, which gave 20 million euros ($23 million) in aid in 2015, says it is "critical of the democratisation process".
The Commonwealth sent observer missions for the last three elections, but has not sent a team this week, although the Southern African Development Community bloc and African Union will deploy monitors.
After the 2013 vote, the Commonwealth's experts reported they "cannot conclude that the entire process was credible."