The Expressway Authority of Thailand (Exat) intends to reclaim 11 locations, which have been leased to City Hall, for a new expressway project worth 31.2 billion baht.
They will include the parking area of a public park along the banks of the Chao Phraya River, under Rama IX Bridge in the Phra Nakhon and Thon Buri areas.
The park, which covers 29 rai of land and was opened in 2000, was built in commemoration of the 72nd birthday of the late King Bhumibol Adulyadej.
Deputy Bangkok governor Chakkaphan Phewngam said on Monday that Exat planned to reclaim 11 locations across Bangkok for construction of the Rama III Road-Dao Khanong-Western Outer Ring Road Expressway, which is expected to stretch about 17km.
The project would form an effective road link between the inner city and outer areas of Bangkok, he said.
The 11 locations currently house small-scale fire stations, short cuts in the city, public parks and exercise venues, all operated by the Bangkok Metropolitan Administration (BMA).
Apart from the areas under Rama IX Bridge, other locations which will be returned to Exat include two small fire stations in Bang Phongphang and Pracha Uthit.
City Hall needs to seek new locations for both fire stations as well, Mr Chakkaphan said, adding the agency's assets and properties must be moved from the 11 locations by Sept 30.
Earlier, a group of residents also sealed off the park under the Rama IX Bridge in protest against the demolition of the park to pave the way for the expressway construction.
Exat agreed to reclaim only two out of the 29 rai after a discussion with the Bangkok Metropolitan Administration which was concerned the project will affect people who use the park, he said.
Mr Chakkaphan said if the two rai of land, which serve as a parking lot, are reclaimed, residents who travel to the park by private vehicles will be affected.
City Hall is currently conducting a survey around the park to find a suitable location for a new parking lot, he said.
According to Mr Chakkaphan, the park currently accommodates about 1,220 people a day during Monday to Friday and about 1,550 people a day at weekends and public holidays.
Responding to public feedback on the park, Exat governor Narong Kieddej insisted only 3.4% of the park's 29 rai will be returned to Exat.
The project will not affect the green zone of the park, he said.
The park will operate as normal while people will be allowed to use the parking lot until the area is declared off-limits as construction machinery will be stationed there.
The construction of the expressway project will begin within this year. It is expected to be completed in 2021, Mr Narong added.
Thanongsak Manothamraksa, a resident, said he did not oppose the expressway but he did not think it was necessary to close the park which caters to many people who exercise or play sport.