The two firms said the price reductions will take effect at 5am on Friday.
But diesel oil price will remain unchanged at 34.94 baht per litre.
The new rates will see petrol stations in Bangkok sell petrol at:
Non-gasohol benzene: 48.96 baht
Gasohol 95: 41.55 baht
Gasohol 91: 41.28 baht
E20: 40.44 baht
E85: 35.34 baht