Two major political parties raised doubts on Monday about the fairness of Thailand’s election results amid growing complaints about irregularities during Sunday’s poll and a vote count marred by hiccups and confusion.

Early unofficial results announced by the country’s election commission in the first poll since a 2014 military coup gave the pro-army Phalang Pracharat party a larger share of the popular vote but the main opposition Pheu Thai, aligned to Thaksin Shinawatra, the exiled former leader, the biggest seat count.

However, the commission has yet to release information on 150 seats allocated to the 500-strong lower house under proportional representation, and has been strongly criticised for delaying the publication of the full results.

The lack of clarity has resulted in the two rival camps both declaring their intention to form a coalition government and in growing suspicion over attempts to rig a poll which is already stacked in favour of pro-junta forces.

Mr Shinawatra told AFP on Monday that he believed the vote was "rigged" and marred by "irregularities".

"If rules and the referee is not fair," he said, "the result will not be respected."

With Pheu Thai currently on 138 seats in the House of Representatives and Phalang Pracharat, led by junta chief General Prayuth Chan-o-cha, on 96, any coalition is likely to be fragile and unable to push through legislation.