The 245m elevated walkway, or skywalk, will serve commuters in the Phasi Charoen area, said Amorn Kitchawengkul, deputy Bangkok governor.
It will link Bang Wah station, the last BTS stop on the Thon Buri side, and Taksin-Phetkasem pier, he said. The skywalk will also cross Khlong Phasi Charoen.
Mr Amorn said the infrastructure will maximise the efficiency of the city's public rail and water services.
The move comes after the successful launch of a pilot boat service project on Khlong Phasi Charoen by the Bangkok Metropolitan Administration in late April. The service operates at canal-side communities in Thon Buri.
With 10 boats in service, the 11.5km-route now runs daily from Pratunam Phasi Charoen Pier to Phetkasem 69 during the morning and evening rush hours.
The service attracts more than 2,000 passengers each day, Mr Amorn said.
"That reflects the practicality of the boat service [linking the BTS] and the demand for public transport penetrating into the community," he said.
The next phase of the boat service would extend operating hours in the evening, he said.
Eventually, more boats would be added, a move expected to attract more than 3,000 passengers daily, Mr Amorn said.