The results of Sunday's general election will now be announced on Monday at 10 a.m. (0300 GMT).
It was not clear how many seats Palang Pracharat would have in the House of Representatives, as the Election Commission said it would only release the winners of 350 seats on Monday.
If the pro-military faction does take control of the new parliament, as most consider likely, operating under a democratic system may be a test for Prayut and the military, who are not used to having any political opposition while in power. This means that the military only needed 126 votes in the lower house to bring back the head of the junta, Prayut Chan-ocha, as prime minister.
The Pheu Thai party has also voiced concerns and wants to inspect disqualified ballots, which are more than a million in number.
He compared Thailand to Myanmar and Indonesia during their years of military-led quasi-democracies.
But Shinawatra-linked parties have won all elections since 2001, and they are projecting to win 150-200 seats.
Mr Thaksin was referring to the commission's chairman Ittiporn Boonprakong, who when asked on Sunday what the final results would be after the announcement that the results would be delayed, said, "I don't have a calculator with me now".
That is almost half a million more votes than Pheu Thai, which nonetheless was confident Monday it would still win the majority of lower house seats.
Alternatively, the constitutional court may choose to disband Future Forward after the election, or the Electoral Commission may choose to red card enough MPs so that the minimum quorum of parliament may not be reached, and parliament can not be opened.
Pro-army Palang Pracharatarty spokesperson Kobsak Pootrakool told reporters it has planned to form a government after winning votes in the nation's first election since 2014 coup.
With 95 per cent of votes counted as of last night, the pro-junta party grossed 7,939,937 votes nationwide while the Shinawatra-backed Pheu Thai was second with 7,423,361 votes.
"We have received the most votes of all the parties that were running in the election", he told Al Jazeera in an interview at the party's headquarters, adding that they were in the process of building a coalition of like-minded parties.
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With strong support from first-time voters it became the third-ranked party by votes.
Mr Thanathorn energised numerous seven million first-time voters by vowing to end military "dictatorship" and tackle Thailand's inequalities.
The new constitution allows parliament's upper house, the 250-seat Senate, to vote with the 500-seat lower house to choose the prime minister.
"Without vote buying, we wouldn't have suffered such big losses", said candidate Sirichok Sopha.
As Thai voters select their next government in the wake of nearly five years of direct military rule, critics have slammed the voting system, accusing the junta of rigging results to favor pro-military political groups.
As rivals scrambled to seize the momentum and persuade other parties to join forces in a coalition, Thaksin - who had remained tight-lipped in the months running up to the vote - hit out at the junta.
Of course, we may also see protests by people unhappy with the rigging of the election by the people.
Thaksin has lived in self-exile since 2008, but he looms large over Sunday's election.
The vote has again revealed Thailand's old divisions between Thaksin supporters and arch-royalist, conservatives who look to the army for stability.
Prayut toppled the civilian government of Thaksin's younger sister Yingluck in 2014, the twelfth coup in under a century.
On the eve of the vote, King Maha Vajiralongkorn made an unexpected and cryptic statement, recalling a comment made by his late father in 1969 on the need to put "good people" in power and to prevent "bad people from. creating chaos".