Ko Mak, not to be confused with the more popular Ko Mak Island in Trat Province, is a sub-district in Phak Phayun District of Phatthalung Province. It is also an island, as the Thai name states, connected to Pak Phayun by a bridge at the southern end but this one located in the massive Songkhla Lake. Ko Mak, about 18 kms long and barely 3 kms wide is sparsely populated and lies opposite the Khu Khut Waterfowl Park in Sathing Phra district of Songkhla province. The north-eastern tip of the island is also wetland and a wildfowl refuge while picturesque hamlets exist using resources from the lake. Drop nets known as 'yor' are a reminder of the reliance on lake fishing and create magical photo opportunities while peace and tranquillity lies all around.
Another source of income for local people is described by Wikipedia:
'The gathering of edible bird's nests is a significant contributor to the local economy. The state auctions off concessions to private firms for the right to collect bird's nests, largely in Ko Mak Sub-district. The province earned 450 million baht in the latest five-year concession auction for nests harvested from caves, primarily on Ko Rangnok ('Bird's Nest Island'), down from the 100 million baht a year earned in previous auctions. In decline also was the quantity of edible nests collected in Ko Mak. In 2017, 3.46 tonnes of nests were gathered, dropping from 3.6 tonnes in 2016. Bird's nests taken from the caves in Ko Mak can fetch 120,000 baht per kilogram, and when exported to China the price can reach one million baht per kilogram.'

Source: Onsite visit and Wikipedia