The investigation was ordered after images of the high-rise condominium, currently under construction, were posted online with a message urging the National Council for Peace and Order to investigate.
The campaign has drawn support from many netizens.
The message claimed that the 53-storey condominium at Laem Bali Hai in Chon Buri, South Pattaya, blocks the view of the beach from the popular viewpoint Phra Tamnak Hill.
A statue of HRH Prince Chumphon Khet Udomsakdi was built on the viewpoint overlooking Pattaya.
ONREPP secretary-general Kasemsant Jinnowaso said an initial investigation showed the project's developer submitted an environmental impact assessment (EIA) report to a provincial panel.
The panel approved the EIA report and had already forwarded it to the ONREPP, Mr Kasemsant said.
The office would look into complaints that the project breached EIA criteria by claiming its construction site was further from the beach.
The probe would be completed later this week, he said.
Mr Kasemsant said no EIA criterion states that buildings cannot block beach scenery. If the project was carried out in line with the EIA criteria, the project developer is not at fault, he said.
He questioned the timing of complaints against the condominium as the project is now almost finished.
Bang Lamung district chief Sakchai Taengho said he has coordinated with relevant agencies to investigate the controversial condominium project.
The condominium is being built on a land plot covering two rai, comprising seven land title deeds.
Relevant agencies were examining documents to see whether the project developer had received the correct authorisation, he said.