Sutan Bhatoegana was charged with graft in the process of parliamentary debate on energy budget.
Jero Wacik is already named suspect in a related case.
Both Bhatoegana and Jero Wacik are former chairmen of the Democrat party of former President Susilo Bambang Yudhoyno.
"I am summoned by KPK to testify at the KPK building on Thursday morning.
Jero refused to say more but promised to give details after his investigations by KPK.
KPK also has schedule to question of two former lawmakers of the Democrat faction Natassya Tara and Siti Romlah.
On Wednesday, three other Democrat law makers Efi Susilowati, I Wayan Gunastra and Tri Yulianto, failed to appear to honor the summon of KPK for investigations in the same case.
For Tri Yulianto, the summon on Wednesday was his second.
Sutan Bhatoegana was named suspect implicated by former head of the Upstream Oil and Gas Regulator (SKK Migas) Rudi Rubiandini, who is already convicted and serving a 7 years jail term for graft case.
Rudi Rubiandini said he gave Bhatoegana US$200,000 via Tri Julianto as "Idul Firi allowance" for the lawmakers of the Commission VII of the Parliament.