The haul is worth around Bt24.5 million.
Customs Department director-general Rakop Srisupa-at yesterday identified the suspect as Monica Meere.
She boarded a flight to Bangkok from Johannesburg via Doha. After landing at the Thai airport on Thursday, customs and immigration officials intercepted her in response to a tip.
A search of her luggage allegedly revealed the cocaine inside chocolate boxes.
Meere, 34, has denied knowing that the boxes contained illicit drugs. She said a friend had given the boxes to her to pass to another South African in Thailand.