Police have fined two men and one woman suspected of having sex in broad daylight on a footbridge in Thailand.

Officers made the arrest on Sunday after footage emerged of the trio apparently engaged in a threesome on a pedestrian overpass near a technical college in Phitsanulok province.

The overpass was strewn with garbage and clumps of weed, and is located opposite a condominium, where the footage is believed to have been recorded from.

Sneh Klampoch, 58, a security officer for the unnamed condominium, said the overpass was often used by students and workers.

He said: 'I didn't expect something like this to happen there. The condo's security staff are now monitoring the situation as several tenants also use this bridge.'

Police Colonel Parkpoom Prabsriphum, superintendent of the Muang Phitsanulok police, ordered a team to inspect the scene on February 26.

During the investigation, police found and confiscated a 'love nest' of two dirty pillows and one yellow blanket crammed behind guardrails.

Parkpoom said cops will patrol the overpass and other 'various risky points' as government staff fixes the secluded sex spot in the public area.

Cops later managed to identify and arrest the three suspects, who were fined 500 baht (14 USD) each for lewd behaviour.

Parkpoom said: 'The police were able to arrest all suspects. There were two men and one woman involved. During the incident, they were 'swinging' or taking turns having sex and watching.'

Police Colonel Pakpoom Prabsriphum confirmed that the suspects were arrested and fined.

He said: 'We have warned them not to do this again in public. They will be put in a cell if they're caught doing it again.'