Singapore has one of the most open immigration polices in the world.  But these policies do not currently enjoy popular support.  According to the World Values Survey, Singaporeans seem more anti-immigration than Americans:

Only 4% of Singaporeans favour open borders, and just 24% are willing to
admit immigrants “as long as jobs [are] available”; the comparable
numbers in the United States are 12.4% and 44.8%…

Fortunately, Singaporean elites are very pro-immigration, and the Singaporean electorate treats their elites with great deference.  Hence the Singaporean government’s official long-run plan:

Foreigners now make up about 38 percent of the total population of 5.3 million. In 1990, that figure was 14 percent, when the total population was around 3 million.

Last year, a government policy paper called for the population to
increase a further 30 percent by 2030, to 6.9 million, at which time
immigrants would account for nearly half of the island’s population.

Contrary to popular mythology, Singapore is a democracy.  It’s conceivable that populist pressures will reverse Singapore’s cosmopolitan course, as in Switzerland.  But I’ll bet against it.  As immigration keeps rising, so will the social pressure against nativist complaining.  Deprived of social support, nativist sentiment will atrophy as well.  By the time Singaporean natives become a minority in their own country, nativist hold-outs won’t lament “the country they lost.”  They’ll be too busy pretending they were never nativists in the first place.