Jigme Khesar Namgyel Wangchuck, 31, a mountain-biking fanatic and Elvis fan crowned in 2008, will wed a photogenic student 10 years his junior called Jetsun Pema, the daughter of an airline pilot.
The main wedding ceremony takes place on Thursday in a stunning 17th-century fortress surrounded by mountains and built at the confluence of two fast-running rivers in the ancient capital Punakha.
The newlyweds appear in public for the first time on Saturday at a sports stadium in the sleepy present-day capital Thimphu, where thousands of Bhutanese are expected to turn out in colourful national dress.
The announcement of the nuptials in May broke the hearts of the king’s many admirers — he was once mobbed on a trip to Thailand by weeping teenagers — but it has brought joy to his people, who idolise the royal family.
Cheerfulness abounds on the streets of the country that invented “Gross National Happiness” — a development philosophy that sees the government measure the mental well-being of citizens, not their material wealth.
“I have no words to describe it… I just feel wonderful,” 21-year-old student Chencho Dorji told AFP in Thimphu. “They are the perfect match.”
The only sour note was news of two small bomb blasts in a town on the border with India late on Monday, a reminder of a troubled recent history of ethnic tension in the Buddhist-majority nation.
The explosions were claimed by the United Revolutionary Front of Bhutan (URFB), an insurgent group based in Nepal, which said it had timed the attacks to draw attention to the “gross national sufferings of the Bhutanese people”.
More than 100,000 ethnic Nepalese fled their homes in Bhutan for Nepal in the early 1990s during the reign of the former king, claiming ethnic and political persecution.
Bhutan claims the refugees, mostly Hindus who were forced into camps after being refused entry and citizenship by Nepal, were illegal immigrants.
Wangchuck, who has spoken in favour of religious diversity in Bhutan, is the fifth king from a line of hereditary rulers who have reigned for the last 100 years in inward-looking Bhutan, which is sandwiched between India and China.
The royals are credited with bringing stability to the formerly war-wracked nation and ensuring its independence despite giant neighbours to the north and south, while also preserving the country’s culture and fragile environment.
The biggest recent change came in 2006, when the fourth king abdicated voluntarily to usher in democracy and hand over power to his son, who now rules as a constitutional monarch at the head of an elected government.
Democracy has brought independent media and a new critical attitude towards public servants and the government, but the king remains a figure who is almost universally admired and above reproach.
Tempa Gyeltshen, who is overseeing a team of 40 people preparing the sports ground for Saturday’s festivities, said the marriage was an assurance for Bhutanese people of the continuity of the institution.
“If anything happened to our king, then who would take over the throne?” he told AFP. “What we are all hoping for is children.”
Organisers of the wedding and celebrations have promised the style will be “simple and traditional”.
No heads of state or other royals have been invited, and even Bhutanese ministers have been asked not to bring their wives to the private ceremony on Thursday because of the lack of seating.
Modesty and a “common touch” are seen as part of the core appeal of the royal family and the present king in particular, who lives in a cottage in Thimphu rather than a palace.
The young monarch, who shares a passion for basketball with his wife-to-be, is seen as a modernising influence in Bhutan, which remained in self-imposed isolation for centuries.
The country had no roads or currency until the 1960s and allowed television only in 1999.
Wangchuck will be limited to only one wife under rules laid down in the new constitution. His father married four sisters.