Already one hardware store, so far unnamed by authorities, is under investigation for selling undersized sandbags.
Sandbags that were priced at B55 each were found to contain only 20 kilograms of sand instead of the standard 25 to 30 kilograms.
Police officers have been collecting evidence to file charges against the store.
The Internal Trade Department also found several traders who were not putting price tags on goods, allowing them to indulge in flexible pricing.
Internal Trade Department Director-General Watcharee Wimuktayont said officials have checked prices of goods in Sai Mai, Don Muang, Bank Kane, Lad Krabang and Nongchok districts.
Permanent Secretary Yanyong Puangrat ordered commerce officials across the country to monitor the prices of goods during the flooding.
Customers can report cases about unfair pricing and other hoarding activities via the hotline number 1569.
Home Products Center PLC (HPC), which owns the Home Pro chain, has given assurances that it will peg the prices of its home-repair products in an effort to help people whose homes have been damaged by the flooding.
Khunawut Thumpomkul, Managing Director of HPC said he believes that consumer purchasing power, especially for products used for home repair, will increase after the floods ease.
Mr Khunawut issued an assurance that manufacturers have agreed to freeze building material prices at level they were at before the flooding, in order not to aggravate the plight of flood victims.
He went on to say that the company has also set up a B10 million fund to carry out relief and rehabilitation efforts for flood victims.
The company has also prepared free parking spaces for flood victims’ vehicles at all Home Pro branches.