Another 1,000 sq m at the same land plot will be constructed as a rental gallery to support Silpakorn University students.
Mrs Oranuch expects all construction to finish as scheduled in 2018.
"The CPB has a long-term plan to renovate, adjust and develop the Rattanakosin area until 2025," she said. "The next project will be the renovation of Tha Tien Market and Tha Phrachan's shophouses, likely by 2018."
The three rai of Tha Tien market are closed because of decay and poor sanitation.
The CPB is studying a new design for the two markets.
According to Mrs Oranuch, the renovated locations will include Baan Mot, Mansri, Phraeng Nara, Phraeng Phuthon and Nang Loeng.