A series of coronavirus clusters among construction workers in Bangkok, including the first local cases of the variant first identified in India, has put a fresh spotlight on migrant labour rights as Thailand grapples with its deadliest outbreak so far.

Migrant workers have been crucial during Bangkok's decade-long construction boom, but they receive limited welfare from the government and their employers, advocacy groups say. Many live onsite in crowded dormitories to save money.

Thailand last week detected its first 36 domestically transmitted cases of the highly infectious B.1.617.2 coronavirus variant among people in construction workers' accommodation in Bangkok.

City authorities have prohibited movement of workers at such camps after 11 were among 30 active clusters in the capital, Reuters reports.