Police have released a photo of the woman and a sketch of another suspect, an unnamed foreigner, and issued arrest warrants for them. See this report at Khaosod English.
The following report includes a helpful review of the police investigation up to this point. See the Bangkok Post website for links to related reports and photographs. Also see the Bankgok Post's August 30 report by Terry Fredrickson Police arrest Erawan bomb suspect (Updated Sunday) for a lengthy discussion about the breaking of the case.
By the way events are revealing that the Thai police, who've been the brunt of jokes and complaints about their investigation of the bombing and muddled statements to the press, have been quietly inching their way through a textbook example of thorough police work.
From various news reports, I think they've been getting a lot of help in recent days from American intel analysts and hi-tech surveillance equipment, Interpol, and possibly the British MI6, in a case that by now clearly has a big international component. But gathering and interpreting clues from a complex crime always comes down to old-fashioned slog work.....
Thai woman sought for bomb attacks
August 31, 2015 - 3:47 [local time]
The Bangkok Post
Police believe a Thai woman kept a second safe house for the bombers to assemble explosives
Authorities are hunting for a Thai woman after materials believed to be used for bomb-making were seized from her room at an apartment in Min Buri district. She was believed to know the perpetrators thought to be behind the Erawan shrine and Sathon pier bombings, according to police sources.
The group was thought to be planning more attacks. The woman is identified as "Misaloh", and rented room No.9106.at Maimuna Garden Home, an apartment in Bangkok's Min Buri district.
On Saturday night, a combined police and military force searched the room and confiscated several items which can be used to make bombs. Found in the room include urea-based fertiliser, six 12x7cm bottles of flash powder, black and blue electrical wiring, four wristwatches, a table clock, a pack of bolts, decorative tree lights, an empty box for a walkie-talkie, a radio-controlled toy vehicle and a rucksack containing books. Police seized the items for examination.
The search was based on information gleaned from the foreigner suspect detained on Saturday in a raid at the Pool Anant apartment in Nong Chok district, where authorities seized bulk supplies of materials for making bombs, sources said.
The suspect is now being detained at the 11th Army Circle in Bangkok. Following the Saturday night search, a team of 40 police and military officers went back Sunday to to Maimuna Garden Home and searched the entire apartment again. A welding tool was found in one room and seized for examination. Deputy national police chief Chakthip Chaijinda said police were deployed to five areas to track down more suspects. He declined to disclose the locations.
Police spokesman Prawut Thawornsiri said Sunday a network of foreign nationals is thought to be behind the Erawan shrine blast.
Pol Lt Gen Prawut said significant quantities of bomb-making materials including detonator cords and fuses seized from the suspect's room during Saturday's raid point to the possibility the suspect and his accomplices had several more targets in mind.
"There were large quantities of bomb-making materials including 10 detonator cords," said Pol Lt Gen Prawut, also assistant police chief.
The evidence has been sent for forensic examination and the findings will confirm if they are linked to the Erawan shrine and Sathon pier explosions, he said. The police spokesman said the detained suspect, who cannot speak Thai, has so far denied any involvement in the Erawan shrine bombing, he said, adding authorities cannot confirm his identity or nationality.
"He gave a certain amount of cooperation, saying where he travelled from. But we don't believe everything he said. So far he has made no confession," he said. Investigators are not ruling out any motives at this stage and it is too early to conclude what role the suspect played in the attacks.
It is believed many other people, some of whom are likely to be Thai nationals, are involved, said Pol Lt Gen Prawut. He did not give a number.
One of the possible motives is the blasts [was] an act of personal revenge after police recently cracked down on foreign criminals including those running fake passport syndicates.
It is possible the suspect is involved in a syndicate that makes counterfeit passports for nationals who entered Thailand on the quiet and wanted to travel to a third country, he said.
More than 200 fake passports were seized from the suspect's room, which lends weight to this theory, he said.
Police investigators have [also] confirmed the two attacks [Erawan shrine and Sathon pier on August 17] are linked based on the type of the explosive devices used.