In the latest twist, the Democrat MP candidate might have beaten the Future Forward contender by four votes in a recount for constituency 1 of the Nakhon Pathom province on Sunday.
An election commissioner observing the recount said late Sunday Savika Limpasuwanna of the FFP might have won by 62 votes with 35,707, trailed by Lt Col Sinthop Kaewpichitof the Democrat Party, with 35,645.
But the Democrat Party later on Sunday challenged the results, insisting their candidate won by four votes.
The Democrats told a briefing on Monday morning according to their calculations, their candidate won 35,711 votes while Ms Savika got 35,707 votes.
This means the Democrat candidate is still the winner but the victory margin narrowed to four votes, from 147 in the EC's March 24 unofficial results.
The EC, however, has not revealed the results of Sunday's recount but deputy secretary-general Sawaeng Boonmee admitted there was a mistake and the provincial EC had asked the two candidates to come check the evidence .
He stressed the problem was not the recount but the filling of a form after it.
Thai media reported the mistake was found in the results of the 25th polling unit, where 66 votes for the Democrat candidate were credited to the candidate of another party, Prachapiwat, leading to the wrong results for the Democrat candidate.
The EC on April 18 ordered the recount for the constituency on Sunday after Ms Savika challenged the EC unofficial results. She claimed to have found inconsistencies between her records -- photos of the results shown at all 245 polling stations -- and the EC's March 24 results and asked the EC to count the votes again.
The recount began at 9am on Sunday. By 9pm, Chatchai Chanpraisri, an EC commissioner who observed the recount, said the FFP candidate led by 62 votes with 35,707, followed by Lt Col Sinthop with 35,645 votes.
Mr Sawaeng explained on Monday Mr Chatchai made the comment based on the data he had at the time, which might have been incomplete.
Thai media reported the mistake was that the 66 votes for the Democrat candidate at the 25th polling stations were credited to a wrong party, Prachapiwat, resulting a wrong total count earlier.