A price index, a market price report, and a shelf price measure different things. Check the date, unit, and type of goods before comparing numbers.
DIT and MOC publish farm-price data. TPSO provides price indexes, while the Bank of Thailand has a retail sales index. GS1 records help identify products. Shop and marketplace prices refer to particular offers. None of these sources alone proves that a shop has an item in stock or will sell it at that price today.
The Ministry of Commerce has an open retail-price data set. It defines the figures as average retail prices at province level. The data is used in work on consumer prices. It is issued each month.
A province average is not a shelf price at one branch. It does not prove that the branch has the item. It also does not prove stock.
The Department of Internal Trade has other price and cost tools. It also handles price-control law and notices. Those rules can change over time.