This is the shocking moment a woman's bag was stolen in broad daylight in Thailand.

Somchok Changchun had placed her backpack on the steps of a building while waiting for a friend at the Soi Phetkasem area of Bangkok on October 18.

As Somchok fiddled with her phone, a woman with a face mask sidled over and snatched the bag off the floor while her back was turned.

The suspected thief was seen casually walking away before breaking out into a jog to catch a bus on which she escaped.

Writing online to ask for help, Somchok said the thief had stolen various items including her driver's license and some money she had allotted for her food stall business.

Somchok said she has frozen her credit cards and filed a report with the police.

She said: 'I was just checking my Line app before going to an event, but my bag disappeared within minutes. I managed to track down the bus, but the woman had already escaped. It's also partly my fault for leaving my bag unattended.'