He said this would be part of the PDRC's operations to be carried out from Monday to retake the people's sovereign power.
The first mission was for PDRC teams to pursue Mr Niwattumrong and other caretaker ministers with a resignation letter for them to sign.
Mr Suthep said that since the country now did not have a government with full authority it was necessary for the people to retake their sovereign power. But this had to be done through peaceful means, not by a power seizure.
After that the sovereign power would be exercised for the country to undergo reforms and attain absolute democracy, he added.
At about 10am, Mr Suthep held a meeting with members of the State Enterprises Labour Relations Confederation and unions from all state enterprises, including the Electricity Generating Authority of Thailand, Metropolitan Electricity Authority and Thai Airways International, at the Santi Maitree building in the Government House compound to discuss an operational plan.
The PDRC will also hold a meeting with retired high-level government officials at 2pm at the same venue.
Akanat Prompan said the main objective of the PDRC was to quickly get a prime minister with full power.
The mission to ask Mr Niwattumrong and other caretaker ministers to resign to return sovereign power to the people would be carried out between May 19 and 21.
"However, if the red shirts show up to protect the ministers, we will avoid clashing with them," the PDRC spokesman said.
On May 22, the PDRC will call a meeting with heads of government agencies to exchange opinions and explore ways out for the country.
The PDRC will stage a final and major uprising to press all sides to cooperate with it, Mr Akanat said.
He affirmed that no government offices would be forced to close, adding that the PDRC's main objective was for all the caretaker ministers to resign. At present, government officials were confused, not knowing if the caretaker ministers still had the authority to supervise the ministries, he added.
Mr Akanat rejected a report that the PDRC would use its demonstrators to lay siege to television stations and government offices.
He said all television stations had cooperated well with the PDRC as previously agreed.
"We are not intimidating the mass media, but they must not act under the influence of the government and the Centre for the Administration of Peace and Order (Capo)," Mr Akanat said.
The PDRC spokesman said all developments in the next seven days would be very important and the PDRC's operations would definitely be concluded by May 26.