The Palang Pracharath Party (PPRP) must submit a report on the fundraising banquet it held on Wednesday, including those who donated more than 100,000 baht, within 30 days, according to Election Commission secretary-general Jarungvith Phumma said.
Mr Jarungvith the poll agency will look into the details after the report is filed but it can launch a preliminary probe if a complaint is made first.
He also played down media reports that some government agencies contributed at the event in which the party claimed to have raised about 600 million baht.
He said state agencies were required to follow strict rules and their spending was subject to audit.
At the centre of accusations was the Tourism Authority of Thailand (TAT) which was reported by some media outlets to have paid 9 million baht for three tables at the Chinese-style feast.
TAT governor Yutthasak Supasorn yesterday strongly denied the reports and called on the media not to drag the TAT into the issue.
He also threatened to sue those media outlets for defamation, saying the TAT strictly adhered to its spending regulations to ensure efficiency and worthiness.
"Based on the regulations, the TAT can't spend in that fashion. Spending amounts are also subject to board review and it has never considered such a donation," he said.
Democrat member Jurin Laksanawisit said the EC would have to examine the fundraiser and determine if state resources were used or exploited in the favour of any political party.
"Using state resources or mechanisms for political gains or advantages is against the law. If no action is taken to establish facts, the public will have doubts and that isn't conducive to the election," he said.
Under Section 76 of the organic law governing political parties, government agencies, state enterprises or any agency in which the state is a major shareholder are barred from making political donations or taking part in such activities.
Section 73 prohibits political office holders from using their positions to solicit funds for political parties or candidates. However, political office holders are not barred from joining fundraising activities.
Deputy Prime Minister Wissanu Krea-ngam said that while state agencies and enterprises are not allowed to make political donations, government officials and state enterprise workers can as individuals.
He said the EC would know best when asked if it was legal for state agencies to persuade private companies to make political donations.
Speaking on the issue of election observation by outsiders, Mr Jarungvith said the United Nations and Asian Network for Free Elections have made inquiries but the EC has yet to consider them.
He said the EC expects to consider such requests after a royal decree announcing the general election is published in the Royal Gazette, adding that requests would likely be granted if they were deemed not to interfere with the country's internal affairs.