Anna Talachava, 30, who works in the tourism industry, told police at the Phuket City Station that the theft took place about 3.30pm at a store in Patipat Road, Phuket City.
Colonel Yongyut Kongmalai said that Ms Talachava had been to visit a friend and was sitting at a table in front of the store, using her mobile telephone as she waited while her friend copied some documents.
A man parked his motorcycle, went into the store for an energy drink, snatched her bag as he went past and quickly rode off.
''Ms Talachava was so surprised she did not get a good look at his face or note the motorcycle numberplate,'' the colonel said.
''Nor did the man who served the thief, her friend's father, get a good look at the man.''
Colonel Yongyut said there was security camera footage of the theft but it was poor quality.
Ms Talachava had her passport, an iPad, 2500 baht, 6400 roubles and some other documents in the bag.