Duangchit Khonthokhonbari, 33, who had been working in Malaysia as a maid, was caught with 2.81 kilogrammes (6.2 pounds) of methamphetamine at Kuala Lumpur International Airport in March last year.
Anyone with at least 50 grams of methamphetamine is considered a trafficker in Malaysia and subject to the death penalty.
Defence lawyers could not be reached for immediate comment, but Duangchit is expected to appeal against the death sentence, which is carried out by hanging in Malaysia.
The verdict comes just days after an Australian mother-of-four, Maria Elvira Pinto Exposto, was also charged with drug trafficking in Malaysia.