More crude oil has spilled from the same underwater pipeline owned by Star Petroleum Refining Plc (SPRC) off the Rayong coast.
Rayong governor Channa Iamsaeng said Thursday's leakage occurred near previous pipeline breaches.
He said the amount of leakage has not been determined although oil containment booms have been put in place to prevent spill expansion.
The Marine Department has also deployed ships for spraying dispersant chemicals on the spill.
Mr Channa criticised the company for not implementing adequate prevention measures, which has led to repeated accidents.
On Jan 25, 47,000 litres of oil leaked from an SPRC pipeline. Another 5,000 litres leaked earlier this month.