Which is the cheapest way to transfer USD10k from US bank account to SGD?

You can try instarem as well :)

Yes Transferwise is currently the best, safe snd cheapest.

Of note one can not only convert/transfer to countries abroad but also works within a single country. Should always be used if one buys equity in a non SGD currency with a SG bank or broker because they charge almost invisible fees with their automatic conversion.