The State Railway of Thailand (SRT) will sign a contract with a contractor to lay 13.3km of rail track for the Ban Pho-Phra Kaeo section in Ayutthaya province this month.
The new track will be part of the Sino-Thai rail project from Bangkok to Nong Khai.
SRT governor Nirut Maneephan on Monday gave updates on this section, which has a construction budget worth 10.3 billion baht.
Mr Nirut said the SRT is awaiting a draft contract from the Office of the Attorney-General (OAG) to start construction.
He said the SRT will sign the contract with its contractor, Boonchai Panich (1979) Co Ltd, within this month before issuing a notice to proceed.
Meanwhile, the Heritage Impact Assessment (HIA) on the design for the elevated rail track at the Ayutthaya station, about 2 kilometres from the province's historic sites, has been sent to nine internal agencies and Unesco headquarters in France for approval.
Mr Nirut also spoke on how the project's Bang Sue-Don Mueang section is undergoing a negotiation between the SRT and the contractor over a route overlapping the Don Mueang–Suvarnabhumi–U-Tapao high-speed railway.
The resolution will be proposed to the Eastern Economic Corridor Office of Thailand (EECO), and decisions will be finalised by the end of this year, he said.
"It is likely that the SRT might undertake the construction contract itself to avoid a delay in the project," said Mr Nirut.
When asked about the source of funding to finance the railway construction, Mr Nirut said that the SRT has to consider if it will apply the budget from the Thai-Chinese high-speed train project, the Don Mueang–Suvarnabhumi–U-Tapao high-speed railway, or a loan which the cabinet must approve.
The SRT plans to propose the budget acquisition to the cabinet this year. Mr Nirut added that the first phase of the Thai-Chinese high-speed line, the Bang Sue-Don Mueang section, will be ready for service in 2028 as planned.
The total budget for the Thai-Chinese high-speed train project is set at 179 billion baht, which includes two phases, Bangkok-Nakhon Ratchasima and Nakhon Ratchasima-Nong Khai, covering 606 km across eight provinces.