The extension runs Aug 1-Jan 31.
The free-travel scheme covers 800 non-air-conditioned buses on 73 routes in Bangkok and 172 third-class inter-provincial train services.
The meeting also agreed to extended the term of the diesel excise tax reduction to 0.005 baht per litre for another month, until Aug 31.
The NCPO earlier announced diesel price would be kept at below 30 baht per litre until a reform of the oil-price structure is done.
The diesel excise tax is currently set at 0.005 baht per litre, resulting in losses to the government of 9 billion baht monthly and 180 billion baht annually.