* IRPC may now push shutdown to later in August or October

* Energy ministry asks Thai Oil, IRPC to raise output

* Bangchak shuts 120,000 bpd refinery after fire (Combines Thai Oil, IRPC stories, adds details)

BANGKOK, July 4 (Reuters) - Thailand's IRPC Pcl will postpone a late July refinery maintenance shutdown and Thai Oil Pcl may do the same to help avert supply shortages after a fire on Wednesday at a refinery operated by Bangchak Petroleum Pcl.

PTT Pcl is the parent company of both IRPC and Thai Oil.

"PTT group will seek more supply from domestic refineries, including a plan to delay IRPC's maintenance shutdown, and may consider imports," PTT Pcl said in a statement.

IRPC, which has capacity of 215,000 barrels per day (bpd), had a major shutdown in the fourth quarter of 2011.

It had planned a shutdown, this time not involving major units, from July 20 to Aug. 7. It may now push that to later in August or October, President Atikom Terbsiri told Reuters.

IRPC currently runs at about 180,000 bpd.

Thai Oil, the country's biggest refiner, could also postpone a shutdown planned for Aug. 1 to Sept. 7 if there proves to be a shortage of fuels, the Energy Ministry said.

This shutdown wasn't planned for any major units, Thai Oil said. It has said it may undertake major maintenance for a month in the second quarter of 2013.

The ministry has asked Thai Oil and IRPC to raise output and expects they can produce an additional 35,000 bpd to help offset the shortfall caused by the Bangchak fire, Energy Minister Arak Chonlathanont told reporters.

Bangchak produces around 99,000 bpd, accounting for 9.9 percent of Thailand's total output of 1 million bpd. The country has enough reserves to meet demand, the minister said.

Bangchak declared force majeure on crude imports after the fire, which broke out early on Wednesday but was brought quickly under control.

Bangchak has shut the 120,000 bpd plant for a week as the fire damaged a crude distillation unit.

That unit, with a capacity of 80,000 bpd, will remain shut for at least 30 days, while the smaller 40,000 bpd unit and a hydrocracker unit will be restarted after a week, President Anusorn Sangnimnuan told reporters.

The shutdown of the bigger CDU may extend to two months, he added. (Reporting by Wilawan Pongpitak, Khettiya Jittapong and Apornrath Phoonphongphiphat; Writing by Alan Raybould; Editing by Manash Goswami and Jason Neely)