The demolition of the mansion in Chonburi's Bang Lamung district was ordered as its Building A was found to be encroaching on public land, while two other buildings -- Building B and Building C -- were built without permission.
The Building C area has been cut to comply with laws related to distance from the sea. Action on Building B is pending a decision by the court.
On Tuesday, 30 officials from Pattaya City municipality turned up at Sukhawadee House with backhoes and trucks.
Building A was constructed t on an 11-rai plot reclaimed from the sea. It forms part of the 80-rai plot on which Sukhwadee House stands.
Initially, the officials dismantled floor tiles and cut water and electricity. The lawyer representing Sukhwadee House came to observe and ask the municipality to slow the demolition.
Chris Cherdsuriya, head of Pattaya City engineering office's building control department, said the city municipality had ordered the owner of Sukhwadee House to demolish the building but no progress had been made to date.
The time had therefore come for the city of Pattaya to take action, otherwise officials could face punishment for neglecting their duties, he said.
He said the officials will take up to seven days to ensure that the owner cannot utilise it, before hiring contractors to demolish the whole building.
He added that the city municipality will demand demolition expenses from the proprietor, Panya Chotitawan, owner of Saha Farms Co Ltd, one of the country's largest frozen poultry exporters.