The Palang Pracharat pro-military party received an estimated 7.5 million votes — an amount that is currently just shy of an absolute majority — against some 7 million votes for the main opposition party, Pheu Thai.
According to local reports, about 80 percent of the southeast Asia nation's 51.4 million electorate took part in the vote, the first political referendum in Thailand since the military seized control of the country's government in a 2014 coup.
"It will be clearer once the official result is announced," Wechayachai said, cited by Deutsche Welle.
The results of Sunday's general election will now be announced on Monday at 10 a.m. (0300 GMT). No explanation has been provided for the delay, originally scheduled for 8:30 p.m. (1330 GMT) Sunday.
The weekend elections saw a last-minute Saturday admonition from the nation's king, Maha Vajiralongkorn, who warned that voters must follow "good" leaders as a means of preventing "chaos."
As Thai voters select their next government in the wake of almost five years of direct military rule, critics have slammed the voting system, with accusations of rigging results to favor pro-military political groups.
Over 7 million new voters have been added to the electorate since the last elections in 2011.