Thai voters are defying enforced reverence for their sacrosanct monarchy in a country where criticism of the king is considered treasonous.

The mood of a majority of Thai voters has prevailed in elections for the lower house of the parliament in which the opposition Move Forward Party and other groupings crushed the party of the prime minister, a general who rose to power in a coup nine years ago.

The leader of Move Forward, Prem Limjaroenrat, was so exhilarated by the success of his party that he immediately laid plans for a “coalition” government — of which he would become prime minister.

In the political maze of a country in which shifts of power have regularly been decided by coups d’etat since the old absolute monarchy was replaced by a constitutional monarchy in 1932, another seismic shift now appears possible.

The government of the leader of the United Thai Party, Prayuth Chan-ocha, finished fifth in the voting with just 36 seats in the 509-member house of representatives of the congress. He faces what might seem as overwhelming opposition from a coalition that controls more than 300 seats.

Hang on, though: General Prayuth can count on support from the upper house or senate, whose members are all appointed by the government. With the senators behind him, he may still try to block 42-year-old Mr. Prem’s way to power since he’s got to win a total of 376 votes from both houses.

That obstacle did not dampen Mr. Prem’s confidence after the election in which his party won 151 seats. A coalition should still assume power as quickly as possible, he said, so “the people, not the military, decide their future.”

He was especially encouraged by what had seemed like a vote of total confidence from the Pheu Thai, the party that came in second at the polls.

The Pheu Thai leader, Paetongtarn Shinawatra, the daughter of a former Thai prime minister, Thaksin Shinawatra, whose party had been expected to finish first, promised to work with Mr. Prem and other party leaders.

They both reportedly congratulated one another for their showings at the polls, and Mr. Prem asked her to join his government. Much will depend on the future of her father, who was overthrown by the military in 2006, lives in exile, and faces a jail sentence for abuse of power and corruption if he ever gets back home.

The election on the surface revolved largely around the issue of a flagging economy, but opposition political leaders have also been calling for revision of the lèse-majesté law under which the courts can impose drastic penalties on those convicted of speaking ill of the king, much less of defying him.

The law was rigidly enforced during the long reign of the popular King Bhumipol, who died in 2016, but questions have been surfacing openly since his son, King Maha Vajiralongkorn, succeeded him after his death nearly seven years ago. 

Activists have gone so far as to call for an end to the monarchy, or at least for an end to the ceremonial rule of King Maha. Now 68, one of the world’s richest monarchs, with a fortune of nearly $40 billion, he spends much of the year in Germany.

Mr. Prem, however, said the future of the monarchy was not on the agenda while attempting to get a new government installed over possible opposition from the military leaders, who hold the real power through the armed forces, the police, and other defenders of monarchical rule.

Such is the power of the lèse-majesté law that a classic Rodgers and Hammerstein musical, “The King and I” — about a 19th century monarch, King Mongkut, a.k.a., King Rama IV, and the English woman who tutored his many children — is banned in both its stage and movie versions.

That does not mean, though, the show is unknown in Thailand. In central Bangkok, a massage parlor is named “King and I,” an act of lèse-majesté that does not seem to have caught the attention of authorities.