Public health permanent secretary Narong Sahametapat said late Tuesday that the 24-year-old woman, who returned recently from Guinea, would be tested again on Thursday with final results known this week.
Apichai Mongkon, director-general of the Department of Medical Sciences, said the woman was first tested in China and the second was made in Germany. The most-recent blood samples were checked at the Department of Medical Sciences and Chulalongkorn Hospital.
When she was hospitalised, the woman was running a fever of 38.8 degrees C, a sore throat and runny nose, said Sopon Mekthon, director-general for the Department of Disease Control.
The case was reported to the ministry on Monday and she was kept in isolation at a state hospital.
A surveillance and rapid-response team at the DDC has found 16 people who have been in contact with the patient. None of them showed similar symptoms. All will be monitored for 21 days, however, in line with Ebola-surveillance measures.
The deadly virus has killed a confirmed 1,546 people in West Africa, according to the World Health Organisation. The outbreak is centred on Guinea, Liberia, Nigeria and Sierra Leone.
The ministry cleared another woman on Aug 22 after monitoring her for suspected Ebola infection. Her blood tests proved negative. The woman had worked in Liberia and returned to Thailand on Aug 20.