Suthep Thaugsuban led anti-government protesters to the MWA head office on Pracha Chuen Road and was welcomed by official staff, some putting up banners to support the PDRC rally for reform and to unseat the caretaker government.
PDRC spokesman Akanat Promphan said the ''visit'' was aimed at convincing state-enterprise officials to come out and join its rally.
Mr Suthep thanked them for their show of support and encouraged MWA staff to be part of the fight to end the Thaksin regime, before returning to his protest base at Lumpini Park.
The rally at the MWA was joined by members of the State Enterprises Workers Relations Confederation.
The MWA visit follows the anti-government group's visit to another state enterprise, the Government Pharmaceutical Organisation, on Thursday, when they were also warmly welcomed.
The PDRC will resume its rally at other state-owned agencies on Monday.
State enterprises are the main destinations for the PDRC in its campaign after the Songkran holidays.
It announced it would visit more agencies to put pressure on the government until the Constitutional Court rules on the fate of Ms Yingluck for the unlawful transfer of Thawil Pliensri from the National Security Council to an inactive position as PM's adviser and the National Anti-Corruption Commission decides on her alleged dereliction of duty in the rice-pledging scheme.
The Supreme Administrative Court ruled last month that the transfer of Mr Thawil was unlawful and an abuse of power. A group of senators subsequently petitioned the charter court to disqualify her.