The general manager and the civil engineer in charge of the construction of a seventh storey were also arrested, the Deputy Interior Minister, Chamicsami Sakdiseth, said. Two other shareholders were being sought.
The death toll in the Royal Plaza Hotel disaster passed 100 yesterday with more than 50 still missing in the wreckage.
More than 270 people were injured when the hotel collapsed. Some 95 remained in hospital. The bodies of 22 people were found in the coffee shop of the hotel late on Saturday. Among the dead was a British woman, Jay Mawdsley.
Officials said the 134-room hotel, in a town 250km (150 miles) north-east of Bangkok, was originally a two-storey structure to which four storeys had been added. Another floor was under construction.
Rescue workers stopped using heavy equipment where they thought survivors were trapped, but began using cranes again elsewhere in the rubble despite objections that they were putting lives at risk from cave-ins. Thai doctors yesterday began amputating the crushed legs of trapped survivor Maneewan Chittisaksopon, a hotel employee, but could not remove the beam pinning her in the ruins. Rescuers had dug with their hands for seven hours to try to free her from beneath the rubble. Mrs Chittisaksopon was found as she called out for her husband from beneath the debris.
Later another female survivor was found but first efforts to free her from the hotel wreckage were unsuccessful.
The hotel collapse was the latest in a series of disasters in Thailand, including a factory fire in Bangkok that claimed 188 lives in May. Exit doors of the factory were locked. Commentators blame many of the recent disasters on corruption.
Prime Minister Chuan Leekpai toured the site and said he had ordered the provincial governor to conduct a full investigation.
'Our people so often break the rules. This is why so many problems occur,' he said earlier.
The Prime Minister said he had heard a report that large amounts of water had been pumped into two new tanks on the roof of the hotel because the city was experiencing periodic water shortages.