All foreign visitors must ensure that they meet or possess the following entry requirements stated the Singapore Immigrations and Checkpoints Authority. US Passport Holders (regular, official and diplomatic) do not require a visa to enter Singapore for business or for social visit purposes.They must, however, meet the entry requirements as mentioned above.ll foreign visitors must ensure that they meet or possess the following entry requirements stated the Singapore Immigrations and Checkpoints Authority. US Passport Holders (regular, official and diplomatic) do not require a visa to enter Singapore for business or for social visit purposes.