Huge amounts of electricity are needed to power the vast computer farms that mine for cryptocurrency such as bitcoin, leading to heavy criticism of its impact on the climate.
Police on Wednesday swooped on a disused ice factory in western Samut Sakhon city after being tipped off about suspiciously high electricity usage.
"We found up to 690 (bitcoin-mining) units," Samut Sakhon City Police chief Pichetpong Changkaikhon told AFP, worth an estimated $1.9 million (69 million baht).
Other seized items included an electrical transformer, laptops and aluminium cables.
A Myanmar national was arrested on site with police still investigating a number of figures, including the factory owner and property leaseholder.
Pichetpong said there had been other raids targeting bitcoin mining in the city, but nothing on this scale in one location.
"There were other places raided too for illegal bitcoin mining but we found only 40 to 50 bitcoin mining units," he said.
Last week, officers from the Technology Crime Suppression Division raided two locations – part of a Chinese temple in Ratchaburi and a warehouse in Samut Songkhram – where 187 and 465 bitcoin mining machines were seized respectively, worth an estimated $5 million.
Illegal bitcoin mining is on the rise in Thailand but requires huge amounts of electricity, with police often tipped off to the activity by massive power surges.