The blaze started at midnight inside the building and was still raging twelve hours later.
Eleven fire engines and 360 people were part of the rescue operation.
- We are trying to get the dead out right now.
I don't think there will be any survivors because of the thick smoke.
We have to have full equipment to be able to breathe at all, says one of the rescue workers.
Videos shared online show flames flickering in the large complex and people on rooftops and at windows shouting for help.
A person is seen falling.
The building complex is 14 floors at most.
Thai fire brigades are participating in the rescue work, according to a source in the Thai Ministry of Foreign Affairs.
Photo: Stringer
13 people receive intensive care
Over 50 injured have been admitted to hospitals in Thailand and 13 of them are in intensive care, according to the medical management.
According to the governor of Thailand's Sa Kaeo Province, 79 Thais, 30 Cambodians and eight Indonesians have received treatment for their injuries in the fire.
Thai fire brigades are participating in the rescue work, according to a source in the Thai Ministry of Foreign Affairs.
About 400 people work at Grand Diamond City, which is one of several casino hotels along the border between Thailand and Cambodia.
Officially, Cambodians are prohibited from gambling, and even in Thailand most types of gambling are prohibited.
The casinos in Poipet on the border have many Thai visitors, the resort is only four hours by car from the Thai capital.