BANGKOK, Thailand -- Coup-leader Prayuth Chan-ocha expects his
impressive wins in elections on March 24 will extend his prime
ministry, but anti-junta politicians are struggling to form a
coalition strong enough to challenge him.

Voting results were marred by irregularities and delays but both sides
appeared to win large competing blocks of seats in the House of
Representatives elections.

Attention was now on smaller parties to see which side they would support.

The most stunning victory by a smaller party was Thanathorn
Juangroongruangkit's rebellious Future Forward.

They promised to punish future coup leaders, end army conscription,
slash the military's budget and rewrite Prime Minister Prayuth's 2017

Mr. Thanathorn is a 40-year-old scion of a wealthy family
manufacturing automobile parts, and attracted most of his support from
younger voters.

They were fed up with their parents' inability to stop Thailand's
U.S.-trained army from launching a dozen coups since World War II in a
bloody cycle of putsches and pro-democracy protests.

Also surprising was mid-sized Bhum Jai Thai party's strong wins.

Its conservative leader Anutin Charnvirakul rapidly gained popularity
in this agricultural nation by demanding recreational marijuana be
legalized so farmers could profit from a cash crop bigger than rice,
sugar or rubber.

After Mr. Anutin said he would join any party which accepted his
platform, his Bhum Jai Thai became a prize sought by both sides.

Mr. Prayuth recently legalized medical marijuana but refused to allow
the public to grow the plant for personal or commercial use.

If Mr. Prayuth's Palang Pracharat party's final tally totals at least
126 House seats, or he attracts other parties, he could add his 250
junta-appointed Senate seats to secure a required 376 seats to remain
prime minister.

The opposition Pheu Thai party was the biggest anti-junta winner. But
they need a 376-seat coalition entirely from the House because the
Senate was expected to reject them.

As a result, Pheu Thai's main prime ministerial candidate Sudarat
Keyuraphan was luring other parties in the House which oppose the
military's domination.

Ms. Sudarat's next best hope is to gather a 251-seat House majority
and demand to form a new government.

If allowed, their prime ministerial nominee would then need 376 seats
from the combined 500 House and 250 Senate seats.

It was not immediately clear if the Senate would remain neutral to
give Mr. Prayuth's opponents a chance to govern, or clobber them with
its 250 seats to create an unbeatable majority for him.

Whoever becomes next prime minister will govern a country polarized by
decades of political unrest, class divisions, widespread corruption,
military interference, and other woes.

Mr. Prayuth, who seized power by toppling an elected government in
2014, would no longer have his near-absolute junta powers and could be
stymied by anti-Prayuth House members.

Alternatively, an anti-junta prime minister could be trumped by a
pro-Prayuth Senate.

If Thailand's next government runs into serious problems or protests,
many fear the army will unleash a coup and again clamp this Southeast
Asian, Buddhist-majority country under military rule.

Meanwhile, allegations of vote buying, fake ballots, lost ballots,
unexplained tally delays, numerical inconsistencies and other
irregularities emerged.

The junta-appointed Election Commission said complaints could be filed
for investigation.

"People now start questioning the credibility of this election,"
Future Forward's Mr. Thanathorn told Bloomberg news on March 25.

"There might be another election, there might be another military
intervention," he said.

Mr. Prayuth, supported by the military, royalists, and many elite Thai
families, staged the 2014 coup to oust the government of Pheu Thai's
Prime Minister Yingluck Shinawatra.

His aim was to stop the influence of Ms. Yingluck's authoritarian,
billionaire brother former Prime Minister Thaksin Shinawatra who the
military toppled in a 2006 putsch.

Mr. Thaksin fled overseas to avoid imprisonment on corruption charges
but he manipulated supporters into electing his allies, including his
sister Ms. Yingluck.

Yesterday's election ignited that confrontation between the military
and Mr. Thaksin who they insist controls current Pheu Thai
politicians, despite their denials.

Allowing them to rule again is unthinkable for many on Mr. Prayuth's side.

Mr. Prayuth's "Palang Pracharat may be able to select the next prime
minister without controlling a majority in the House of
Representatives," Mr. Thaksin wrote from Hong Kong in a post-election
opinion piece published on March 25 in The New York Times.

"But without a majority, the party will be heading a very unstable
government," Mr. Thaksin warned.