Vendors have lined the street with stalls selling food and drink, as well as water guns, plastic bags for smartphones and other equipment for water fights.
The world-famous backpacking street will be closed to traffic from noon to 8pm, Thursday through Saturday (April 13-15) for the Songkran water battles.
The party is forecast to be particularly raucous this week after three relatively dry years under Covid restrictions.
Local businesses expect to see 30,000 to 40,000 Thais and foreigners visit Khaosan on each day of the Songkran holiday, generating about 30-40 billion baht daily. Local hoteliers are reporting occupancy rates of 70%.
A unit of 100 police officers and civil defence volunteers will watch over the revelry this week to ensure public safety among the crowds, said Pol Col Sanong Saengmanee, superintendent of the local Chana Songkhram police station.
Seven screening checkpoints, three first aid stations, four ambulances and three emergency exits have been prepared in the area, he explained.
"Signposts set up in the area carry four languages: Thai, English, Chinese and Korean," he said.
Police would be checking for weapons and smuggled alcohol, the superintendent said. High-pressure water guns, coloured powder, and nudity were also banned at this year’s Songkran parties, Sanong cautioned. People should not dress half-naked, he added.
Bangkok has designated a total of 198 areas across the city for Songkran celebrations. Organised events will feature traditional Thai New Year activities such as sprinkling water over Buddha images, as well as parties, live music and water splashing. Silom Road will not be closed to traffic this year but is expected to be thronged with Songkran revellers for the next three days.