The estimate was announced yesterday by a highly placed source of the EC as the election watchdog races against time to endorse the winners who face no objections within the seven-day deadline after the Senate election.
The March 30 election was to find new senators, one from each of the 77 provinces, to work with the 73 incumbent senators appointed by a committee.
Winners in at least 16 provinces are facing complaints of violating election law; as a result, their senator status is pending investigation.
Under the constitution, the Senate needs at least 95% of its 150 members, or 142 seantors, to perform its duties. The endorsement of the 77 newcomers is thus essential to decide when the new upper house will convene.
But the number of 65 elected senators, if endorsed, plus 73 appointed senators, will not be enough to convene a Senate meeting.
So, the outgoing 77 senators will have to continue in a caretaker role. Today is the last day the EC can receive complaints about the Senate election.
"We set a deadline for receiving the complaints at 10am on April 8 before we start discussing them," said EC secretary-general Puchong Nutrawong yesterday.
The EC is required by law to endorse the first batch of trouble-free senators-elect by tomorrow and complete its endorsement for the rest within 30 days of the election.
Until April 6, Mr Puchong said, the number of complaints stood at 25, but just one day later, the figure rose to more than 30.
Senator-elect Khunying Jaruvan Maintaka, who won the majority of votes in Bangkok, is among the winners facing objections. The former auditor-general was a member of the now defunct Assets Scrutiny Committee established by the 2006 coup makers to probe the wealth of politicians including former prime minister Thaksin Shinawatra.
Other 15 senators-elect facing complaints are from Mae Hong Son, Lampang, Lamphun, Phetchabun, Phrae, Lop Buri, Sing Buri, Samut Prakan, Ranong, Surat Thani, Chaiyaphum, Si Sa Ket, Nong Bua Lam Phu, Amnat Charoen and Ubon Ratchathani, according to the EC source.
It is strange that all the complaints filed with the EC for this Senate poll have noting to do with vote buying, an EC source said. All of them are related to other violations such as a campaigning, which is prohibited for senators.
Some senators-elect face more than one complaint. This will further slow down the process of endorsing the winners. The source expects the EC to decide by April 15 which senators-elect will be disqualified.