A prolific underwear thief who allegedly stole thousands of pairs of knickers for 20 years has finally been caught in Thailand.

Randy burglar Nattawut Songchai, 38, allegedly had a stash of around 600 undergarments before he was nabbed by police at an apartment in Bangkok on February 12.

His arrest came after a female resident from the same apartment reported that the underwear she had hung out to dry had gone missing on February 11 evening, despite the anti-theft mesh screen around her balcony.

Police Colonel Payap Somboon, superintendent of the Bang Yi Khan Police Station, said: 'Investigators examined surveillance footage and found a man walking on the street then climbing up the apartment.

'He stuck his hand in a gap between wall and the metal mesh to steal the underwear. He then returned to his room in the same apartment.'

Officers converged on Nattawut's room and detained him for questioning. They found inside 516 bras, 72 panties, and three sets of women's pyjamas.

Speaking to police officers, Nattawut said he had been stealing women's underwear since he was 18 years old 'because he liked to smell them'.

The pervert told cops: 'I've had a thing for women's underwear since I was 18, back when I worked in construction in Samut Sakhon province.

'At night, I would sneak out of the campsite and snag two to six pairs at a time. I sniffed them while masturbating, and kept my collection a secret from my co-workers.

'I was caught stealing underwear about 10 years ago, but I made a deal with the victim to avoid arrest. I continued stealing underwear after that.'

He said he had been working as a handyman at the Goyee Apartment in Bangkok, where the owner provided him with lodging and a 2,000-baht monthly salary.

Nattawut continued: 'I had been staying there for a year while continuing my habit of stealing underwear until I was eventually caught. I promise I'll quit once I've done my time.'

Officers have now remanded the pervert in custody.

Police Colonel Payap Somboon said: 'He said he cannot stop stealing knickers because he's addicted to it. The court will deal with him and decide what to do.'

Last March, another Thai man was arrested for stealing hundreds of pieces of underwear to pleasure himself.

Ophas Chuenjit, 27, had plucked the bras and knickers from women's washing lines and rubbed them on himself while masturbating. When he was done, he used the undergarments to decorate a bamboo thicket in the woods near his home in Kamphaeng Phet province.

Police detained him following investigations after a shocked passerby discovered the sexual shrine adorned with the soiled underwear.

Stealing underwear is a type of fetish or 'paraphilia' - intense sexual arousal derived from objects, fantasies, or behaviours.

In an interview with the New Straits Times, Dr. Shazli Ezzat Ghazali, Clinical Psychology and Behavioural Health Program Associate Professor at the Universiti Kebangsaan Malaysia, said stealing underwear in particular may make the perpetrator 'feel closer' to the knicker owners.

He added the thieves may feel excitement from committing such taboo activities.