Silom Road will be closed again Wednesday so that Songkran revellers can enjoy themselves, said City Hall's chief adviser Vallop Suwandee.
The closure was originally scheduled to end Tuesday but the Bangkok Metropolitan Administration (BMA) expected more people would join the festival Wednesday, he said.
The area will be closed for a clean-up at midnight so it could re-open for public use Thursday morning, he said.
The 80-metre water tunnel will still be provided but the live performance stage will be closed, said Mr Vallop, adding that bans on alcohol, revealing clothes, and powder will still be in force.
Officials have been deployed at different spots on Silom Road to ensure no one violates the ban, he said.
- [WITH PHOTOS] As residents revel, Police watch their homes
Bangkok governor Sukhumbhand Paribatra inspected seven venues that held Songkran celebrations as part of the Water Festival 2015 along the Chao Phraya River.
The governor ordered officials to check every pier. At least 10 tessakit officials and five rescue staff must be stationed at each pier to ensure safety. Patrol boats have also been deployed.
Meanwhile, Prime Minister Prayut Chan-o-cha praised Thais for being good hosts and boosting tourism.
About 470,000 tourists arrived during the Songkran festival, a 39% increase compared to the same period last year, said deputy government spokesman Sansern Kaewkamnerd.
The industry expects to generate over 7.5 billion baht nationwide during the festival.
Meanwhile, more trains and buses are being added to busy routes as people begin their journeys home from the holidays.
The Songkran long weekend ends Wednesday, when an exodus of travellers is expected, along with heavy road traffic.
State Railway of Thailand governor Wuthichart Kalyanamitra said there is no problem adding train services, particularly on heavy-traffic routes from the Northeast and the North.
Mr Wuthichart said the extra services should help ensure no passengers are left stranded. However, there might be problems with crowding on trains.
In Nakhon Ratchasima, a transport gateway to the Northeast, large numbers of people are arriving at the province's main terminal to buy tickets.
Passengers said they opted to travel a day before the holidays end to avoid the crowds and traffic expected on major roads Wednesday and Thursday.
The office said about 30,000 passengers are expected to pass through the terminal as Songkran ends.