The project required an investment of about $3-4 billion and sentiment in financial markets hads now improved, which could make it easier for the company to get financing, President Kan Trakulhoon told reporters.
"The situation has improved and we decided to hire an adviser. In the past, we had to postpone it because the financial market was closed. If we get some financing, we will move ahead," Kan said.
In March, Siam Cement said the project would be delayed for at least two years because the global financial crisis had made it difficult for the company and its partner, Petrovietnam, to finance the project.
Apart from the petrochemical complex in Vietnam, Siam Cement also delayed two cement projects in Indonesia and Cambodia.
Vietnamese state oil group Petrovietnam and Siam Cement began construction of the joint-venture complex last year in the southern province of Ba Rai Vung Tao.
The first part of the project had been expected to be completed in 2011 and the second in 2013.
At 0457 GMT, Siam Cement shares were up 1.82 percent at 195.50 baht, in line with the overall Thai stock market. ($1=34.00 Baht) (Reporting by Pisit Changplayngam; Writing by Khettiya Jittapong; Editing by Alan Raybould)