Police issued a ban yesterday on high-pressure water guns, dirty water and alcohol in vehicles over Songkran in mid-April.
Pol Gen Chalermkiart Srivorakhan said the move was intended to "boost the confidence of people wanting to celebrate" the traditional Thai New Year, the biggest holiday of the year.
However, police will still allow revellers to ride on pickups while splashing water, the national police chief said.
Police are predicting that tourist sites in the capital will be jam-packed during Songkran, which runs from April 13-16. Places like Khao San Road, Silom and Asiatique will have at least 5,000 tourists each, they estimate.
In the provinces, Khao Niew Road in Khon Kaen, Chiang Mai, and Hat Yai in Songkhla are among the most popular destinations for Songkran celebrants.
Transport Minister Arkhom Termpittayapaisith said 15.4 million people are tipped to travel during the festival from April 11-17.
The government this year aims to cut the number of road casualties during the water-splashing festival by 10%, and trim the number of road accidents by 5%, he said.
The number of holidaymakers behind the wheel is estimated to rise by 3.43% during the Songkran period, while the number of air passengers -- both on domestic and international flights -- is predicted to rise 21.13% this year, he said.
The number of people travelling by public transport -- bus, train and air -- between Bangkok and the provinces is tipped to climb 5.04% over Songkran, Mr Arkhom added.
In a related development, 30 advocacy groups led by the Don't Drive Drunk Foundation signed an MoU yesterday to launch a campaign to raise public awareness of the importance of not driving under the influence.
Dr Taejing Siripanich, secretary-general of the foundation, said such a social movement is needed to reduce road accidents as a top priority.
Thailand ranks first in Asia and ninth in the world when it comes to road casualties, he said.
