From Wikipedia: The term Samsui women (三水妇女; 三水婦女; sān shuǐ fù nǚ) broadly refers to a group of Chinese immigrants who came to Malaya and Singapore between the 1920s and 1940s in search of construction and industrial jobs. Their hard work contributed to the development of the Straits Settlements, both as colonies and later as the new nations of Singapore and Malaysia. Samsui women did manual labour similar to coolies but were more independent.”
Before arriving in Singapore, most Samsui women took vows never to marry, although there have been known exceptions. They lived in cramped conditions with other Samsui women, helping out each other and forming tightly united cliques. Coming to Singapore as cheap labourers between the 1920s and 1940s, Samsui women worked mainly in the construction industry and other industries that required hard labour. They also worked as domestic servants. They had a reputation of rejecting jobs involving drug (particularly opium) peddling, prostitution, or other vices, even if that meant living in poverty. Their contributions to housing construction and as well as labour at hawker centres have been invaluable to Singapore’s early development.