An additional 600 police and Bangkok Metropolitan Administration officers will patrol popular Khao San Road.

The heavy security presence will be obvious from Thursday, a day ahead of the official April 13-17 festival.

"Early birds" are often "enthusiastic" in their activities and police said area businesses were intending to observe the festival from April 12.

Organisers are asking revellers to wear traditional Thai dress and women not to wear revealing attire.

Police and city officials will search bags, patrol for pickpockets and thieves, check motorists for drunk driving and stop motorcyclists without safety helmets.

The city has banned the use of talcum powder and high-powered water guns. Those caught flouting the bans face fines of up to Bt2,000.

Meanwhile, police vowed that homeowners away on holiday could rest easy because of residential patrols.

Royal Police Cadet Academy commissioner Lt-General Pongsapat Pongcharoen said

the academy would deploy 255 senior students to home patrols.

He expects more homeowners to seek the special service while out of Bangkok.

Last year almost 2,100 capital homeowners requested the service, mostly in the Lat Phrao, Khan Na Yow, Phaholyothin, Bang Khen and Don Muang areas.

In Chiang Mai, public transport is prepared for an influx of visitors.

Provincial transport officer Charnchai Kilapeang predicted huge numbers travelling to

popular tourist destinations.

Normally, the province sees 75 inter-provincial bus round trips a day. During the festival that will increase to 100.

Charnchai said a passenger-protection centre would be open to take complaints. Its hotline number is 1584.

Chiang Mai state-rail officer Sompong Buttakhun said trains with additional carriages would run to the province from Bangkok, delivering thousands of passengers.

Local Thai Airways officer Kanchit Reianthong said the airline would put on 22 flights a day from Bangkok to meet demand.