PHUKET police are being sent as reinforcements to Bangkok as concern mounts about the possibility of the red protest inflaming more violence in Thailand's capital and northern provinces.

Phuket Chief of Police, Major General Pekad Tantipong, revealed today that 173 Phuket police officers had been bussed to Bangkok on Monday. The reinforcement police will be replaced every seven days from Phuket in rotation.

''We had no choice,'' Major General Pekad said. He told a media conference at Phuket's Provincial Hall administrative headquarters in Phuket City today that the island will have to cope with a reduced force.

Government buildings on the island are also to be protected around the clock by security from current administrative staff as a precaution against trouble, the Governor, Wichai Praisa-ngob, said today.

Phuket has about 1100 regular police, which means that on any day, allowing for three eight-hour shifts and holidays, the island has about 330 officers on duty. This is an exceptionally low ratio of police to citizens.

Major General Pekad said that the involvement of the volunteer force created to supplement police would be increased. Under Governor Wichai's 'Thousand Eyes of the Pineapple' concept, volunteers equipped with radios patrol many built-up parts of the island after dark.

Phuket has always been under-policed because the number of officers on the island is calculated on the basis of the 320,000 Thais who are registered as Phuket citizens. The number of police apportioned to Phuket fails to take account of hundreds of thousands of other Thais who work on the island and remain registered in other provinces.

With tourists and the estimated 100,000 legal and illegal Burmese laborers, the island's population probably tops one million in some high season months.

There was no sign today of an early end to the red protests that have preoccupied the government, the army and police since the first peaceful banners were waved on March 12.