Abac Poll has vowed not to disclose the results of its surveys about elections in future after its predictions for the Bangkok poll picked the wrong winner.
Abac's pre-election poll, conducted between Thursday and Saturday, had Pheu Thai Party candidate Pongsapat Pongcharoen leading the race with support of 45.9%, an 11% lead over Sukhumbhand Paribatra of the Democrats.
But in the actual election Sunday, MR Sukhumbhand emerged victorious, bagging more than 1.2 million votes.
Noppadon Kannikar, Abac Poll director: "People should not believe everything the pollsters say"
He defeated Pol Gen Pongsapat by about 200,000 votes.
Abac Poll director Noppadon Kannikar accepted the survey results were flawed.
He attributed the discrepancy to respondents later changing their minds, switching from independent candidates to those of the two major parties.
Mr Noppadon stood by the integrity of his poll and insisted the data collected was credible.
"We didn't serve anyone in particular and I'd previously written an article saying people should not believe everything the pollsters say," he said.
Mr Noppadon said Abac Poll would still conduct surveys ahead of future elections but would not publicise the results in case they gave an unfair advantage to any candidates.
The results of future opinion polls would be recorded and used for analysis, he said.
He added that while respondents would still be asked about preferred candidates, the Abac Poll would shift its focus more to key issues surrounding elections, rather than individual politicians.
The poll would also improve its methodology, enlarge the sampling size, overhaul data processing, and attempt to eliminate biased respondents.
Abac was not alone in picking Pol Gen Pongsapat as the favourite.
Suan Dusit Poll, Bansomdejchaopraya Poll and Bangkok Poll also suggested he would win.
In Suan Dusit's entry poll survey, which asked voters about their intentions before they went into the polling stations, Pol Gen Pongsapat emerged as a clear favourite with 49 per cent, compared with MR Sukhumbhand with 39 per cent.
Bansomdejchaopraya Poll and Bangkok Poll also placed Pol Gen Pongsapat ahead of MR Sukhumbhand; by about two percentage points, and three percentage points respectively.
Sing Singkajorn, director of Bansomdejchaopraya Poll, said exit polls may not be accurate since data is collected only at certain times.
Only Nida Poll predicted MR Sukhumbhand would win. Its pre-election poll, conducted between Tuesday and Friday, suggested MR Sukhumbhand would get 43% of the votes, beating Pol Gen Pongsapat by a narrow margin.
The pollsters took flak from many social media users. "Pongsapat won in the last 45 days but lost on the day when it mattered most," said one Facebook comment.
Another message read: "My condolences to the pollsters which sank to their demise when the ballots were tallied and counted."
Another Facebook user said: "This is really the standard of the opinion polls we Thais are accustomed to."