The 670km Thai-Japanese high-speed train project from Bangkok to Chiang Mai is to have its maximum speed lowered to reduce the overall cost of the project.

Deputy Prime Minister Somkid Jatusripitak said Prime Minister Prayut Chan-o-cha has instructed the Transport Ministry to study the possibility of curbing the maximum speed to 180-200kph after a Japanese feasibility study suggested the original goal of 300kph would require a budget of 420 billion baht.

Fares are expected to be 1,200 baht per trip.

In addition, the ministry will also look into whether the project can be implemented as a Public Private Partnership instead of a government-to-government contract as proposed originally, said Mr Somkid. He was speaking after the mobile cabinet meeting in Sukhothai province yesterday.

"Earlier, the [project] was considered worth the investment as it aimed to connect to China via Yunnan but now China has constructed a rail project through Laos and Thailand that will link with the Thai-Sino high-speed train project which will extend to Nong Khai," he said.

"As a result, the Bangkok-Chiang Mai high-speed train project should be reviewed as this project cannot link to other provinces and neighbouring countries," he added.

Still, Mr Somkid said that the government is aiming for construction to start on the Bangkok-Chiang Mai line in 2018.

Transport Minister Arkhom Termpittayapaisith said the first phase of the rail project involves a 380km stretch from Bangkok to Phitsanulok with the budget of about 276 billion baht.

The proposal for this section will be put to the cabinet for approval by March.

Mr Somkid said the cabinet had also ordered the Transport Ministry to review nationwide transport infrastructure development with regards to the needs of tourists.

The existing infrastructure cannot support the traffic between major cities and second-tier tourist destinations which the government aims to promote, he said.