The "horse racing machines" were discovered in an open warehouse located on a 500-rai plot of land on the Lam Luk Ka-Thanyaburi Road. Only three of the 890 units were still functioning as their microchips had not been removed.
Authorities were acting on a tip-off that a large quantity of illegal gambling equipment was hidden on the premises, said Lam Luk Ka district chief Chalermpon Mungkung, who was present during the raid.
The team also searched a nearby facility housing 10 bedrooms for workers, as well as a hall where they found numerous large tables believed to be used for gambling, along with 10,000 sets of cards and some cash.
They also confiscated 10 cars found parked beside a jetski pond and took in the property's 37-year-old caretaker, Somsak Boonsarn, for questioning.
Deputy national police chief Pol Gen Aek Angsananont came to inspect the seized machines and other items at the scene. He said Saturday's operation was the largest seizure since the coup-makers ordered a sweeping crackdown on illegal gambling activities.
Police would carry out further investigations to identify the owners of the machines and the warehouse, he added.