The protection centres for the derelict in only nine of all 76 provinces are free of corruption, with at least 250 ministry officials involved.
The nine provinces are Singburi, Chachoengsao, Prachin Buri, Nakhon Si Thammarat, Nonthaburi, Phrae, Nakhon Sawan, Sukhothai and Uttaradit, according to the Public Sector Anti-Corruption Commission (PACC).
Secretary-general Korntip Daroj said on Monday panels had been set up to look into the irregularities at the centres for the derelict in 43 of the 67 corruption-hit provinces. More will be appointed soon for the remaining affected provinces.
There are 76 centres nationwide, one in each province, and all are under the supervision of the Ministry of Social Development and Human Security. The total budget for the centres in fiscal 2017 was 123 million baht.
"We found 189 ministry officials might have been involved at the 43 centres probed by the panels. We estimate after the panels look into all of them, the number of officials involved could be at least 250," Lt Col Korntip said.
He added the corruption at all centres followed a similar pattern. Officials asked people for their ID cards and used them to forge documents to reimburse welfare money. The cash was then paid to eligible people in part or not at all.
In Singburi, where there is no evidence of cash fraud, corruption was detected in the procurement of blankets, he added.
"We believe centre officials might have talked to one another but there is not enough evidence to indicate it's an organised fraud.
"The perpetrators left no evidence and we could not rule it's one big scheme. We believe it's more of a case where officials might have talked among themselves and copy each other's methods," he said.
After the probe into the centres, the PACC will move on to the third phase, which involves irregularities at self-built communities and development centres for hill tribes people, project coordination centres and cooperatives villages. All of them are also under the ministry.
"We found another 100 million baht might have been stolen from 28 such centres," he said
The PACC plans to complete the investigation into the third phase by the end of July.