The BBC has gained access to where scammers are operating from on an industrial scale.
Almost nothing was known about the Royal Hill casino until the Thai military took control of it in December.
Kuong Li featured in a 2023 BBC Eye investigation into alleged scam compounds in South East Asia.
The release is part of a new ceasefire deal after weeks of deadly clashes along the Thai-Cambodia border.
The ceasefire took effect at noon local time (05:00 GMT) on Saturday.
Almost one million people were displaced when hostilities resumed earlier this month after the first truce broke.
Cambodia accuses Thailand of "indiscriminate attacks", as negotiators meet for a third day to try to end weeks of renewed fighting.
At least 41 people have been killed and nearly one million others displaced on both sides, officials said.
Despite a Trump-brokered ceasefire in July, fighting has flared up again between Thailand and Cambodia.
