Deputy Prime Minister Prawit Wongsuwon will be investigated for possible corruption in failing to report a luxury watch and diamond ring in his declaration of assets and liabilities as required by the anti-graft agency.

Acting National Anti-Corruption Commission (NACC) secretary-general Worawit Sukboon said Wednesday the case has caught the public's attention and the office of the NACC can proceed with the investigation immediately.

He said he would inform the NACC meeting today that the office will examine the issue.

Mr Worawit insisted the anti-graft agency does not feel under pressure because of Gen Prawit's senior role.

The flashy diamond ring and luxurious watch were seen when the deputy premier raised his right hand to shield his face from the sun during a group photo session for the new cabinet on Monday.

As the pictures were shared on social media, some netizens pointed out his expensive jewellery and questioned how he was able to afford such luxury assets despite having only served as a state official.

A Facebook page called CSI LA, popular for its investigative reports, claimed the watch was a platinum Richard Mille RM 002V2 model worth US$370,000.

The Facebook page's administrator also pointed out Gen Prawit's diamond ring is at least five karats, giving it a value of 4 million baht ($122,600) or more, citing over 10 years' experience in the US jewellery industry.

Gen Prawit said Wednesday he was ready to explain the matter to the NACC.

"I will answer to the NACC," said Gen Prawit, who also serves as defence minister. He refused to tell the media when he obtained the watch.

"I have never committed malfeasance. No way," he said.

The Pheu Thai Party has railed against Gen Prawit over the issue.

Acting Pheu Thai deputy spokesman Anusorn Iamsa-ard said the watch was not on the list of assets and liabilities declared by Gen Prawit, who assumed his role in government on Oct 7, 2014.

Mr Anusorn said this could violate the Anti-Corruption Act of 2009.

He said Gen Prawit's assets were recorded as having risen by over 30 million baht from 2008 -- when he served the government of Abhisit Vejjajiva as the defence minister -- to 2014.

Mr Anusorn questioned why the deputy premier's money in his declaration had not dropped if he purchased the watch during that period.

He also noted that if someone had given Gen Prawit the watch, this would have breached NACC regulations, which bar state officials from receiving an asset worth 3,000 baht or more as a gift.

Pheu Thai Party lawyer Ruangkrai Leekitwattana said that aside from the watch and ring, Gen Prawit's amulet necklaces -- worth more than 200,000 baht -- should also have been reported when the deputy premier declared his assets.