BANGKOK — After nearly seven decades on the throne, King Bhumibol Adulyadej, 87, the keystone of Thailand’s identity and a major unifying force for the country, is in declining health. With increasing frequency, the palace has issued medical bulletins detailing his ailments, and in recent days his youngest daughter has led prayer sessions following a Buddhist rite normally used for terminally ill patients.

Worries over the king’s health have cast a pall of anxiety across the country, which has one of the worst performing economies in Asia and is ruled by a military junta that seized power last year.

While reverence for the king was once the only thing that this fractured country could agree on, today the future of the Thai monarchy is uncertain.

The king’s heir apparent, the jet-setting crown prince, has a reputation as a playboy and faces an uphill battle to win the trust and adoration his father has achieved. Many Thais hoped that Princess Sirindhorn, the crown prince’s sister, who has won hearts through her charitable causes and dealings with the poor, might succeed her father, but palace law bars women from the throne.