EXAT governor Suchart Chonsakpipat said his officials would next month announce the terms of reference (TOR) for the bidding of the project, which has a budget of Bt29.926 billion.
He said the contractors would be selected by early next year, provided there were no objections.
The new expressway will be financed by the Thailand Future Funds project.
Suchart said the committee in charge of drafting the TOR would soon meet to adjust the TOR in accordance with public submissions.
The project will be divided into five contracts: a 6.9-km elevated road section costing Bt7.008 billion, a 5.3-km elevated section at Bt7.153 billion, a 5-km elevated section worth Bt6.733 billion, a 2-km bridge costing Bt8.042 billion and a toll collection system worth Bt990 million.