A Perth man and his Thai wife have been sentenced to death in Thailand for trying to smuggle half a tonne of crystal methamphetamine into Australia.

Luke Cook, 34, and Kanyarat Wechapitak, 40, were arrested at Bangkok's Suvarnabhumi airport last December and charged in relation to a 2015 plot to smuggle half a tonne of crystal methamphetamine worth an estimated $300 million into Thailand and then on to Australia.

Australian Luke Cook and his Thai wife Kanyarat Wechapitak. Credit:Narcotics Suppression Bureau

A Thai court has sentenced the couple to death, but that is expected to be commuted to life in prison, media reports on Wednesday said.

A Department of Foreign Affairs and Trade spokeswoman declined to comment specifically on Cook, but said the Australian government was providing consular assistance to an Australian in Thailand.