The pair arrived at the complex in a Bangkok-registered pick-up truck and used loud speakers to repeatedly ask the premier why she was in Saraburi instead of working in Bangkok.
They wanted to know why Ms Yingluck was there on "holiday" while people continue to be killed in protest violence on the streets of the capital.
Another eight PDRC protesters meanwhile arrived at the scene and blew whistles, demanding that Ms Yingluck come out and talk to them since they are taxpayers.
Banyat Wongprayoon, the mayor of Tambon Phu Khae Municipality, tried in vain to convince the protesters to move their demonstration elsewhere. The protesters refused and continued addressing Ms Yingluck through their loud speakers.
This prompted police to come to the complex and prepare to tow away the protesters' vehicles if necessary.
Pol Col Phuban Thapchan, Saraburi deputy police superintendent, said more than 100 policemen were deployed at the OTOP complex to maintain law and order.
He said he would negotiate with the protesters, who were known to police in the province.
Ms Yingluck arrived at the Phu Khae OTOP complex in Chalerm Phrakiat district, Saraburi at 11am. She was accompanied by caretaker Transport Minister Chadchart Sittipunt, caretaker Deputy Education Minister Sermsak Pongpanich and caretaker PM's deputy secretary-general Pol Maj Gen Tawat Boonfueng.
They were received by Saraburi Governor Suthipong Julacharoen.
The prime minister and her entourage left the complex at 12.40pm. Reporters who followed them from Bangkok were told the prime minister had cancelled her other functions for the day.