The EC investigators allege that the nine abused their authority in making electioneering trips around the country prior to the Feb 2 election, which was later nullified, after the house of representatives was dissolved on Dec 9, Matichon Online reported.
It is alleged Ms Yingluck, the seven former cabinet ministers and Pol Gen Adul had used the state's resources and personnel in their trips, ordering government officials to arrange for local people to come out to greet them and raise banners with messages showing support for them.
An arrangement was also made for Ms Yingluck to hand over money to relatives of policemen killed in a clash with anti-government protesters in front of the Thailand-Japan sports complex at Din Daeng on Dec 26.
These activities were designed to give the caretaker government the upper hand in the Feb 2 elections.
Mr Plodprasop said the claims were "nonsensical", and they were only performing the duties of the caretaker government, according to the Matichon report.
He said the accusation against him focused on Dec 12 when he was invited by the Interior Ministry's Disaster Prevention and Mitigation Department to attend a meeting in Chiang Mai on the prevention and control of wild fire. Similar meetings were normal around that time, which was the peak of the bush fire season in the North, and they were attended by all governors and related officials in the region, he said.
Mr Plodprasop also denied that the caretaker government ordered officials to arrange for local people to greet them during the visits.
After the EC investigators decided to take action against them, he received a letter from the EC to appear before it to defend himself against the allegations.
In response, he had already gone to see the EC to clear the allegations, in the belied he had not done anything wrong.
According to him, when asked by the EC what he thought about the allegations his answer was they were "equivocal and nonsensical".