I encountered a Vietnamese money boy on my first trip to Singapore. I also encounter money boys in Pattaya, including non-Thais, who have made short trips to Singapore, taking advantage of the much higher tips on offer. Some make it in whilst their friends get sent back home, as they don't have enough English to complete the immigration form & explain it all away with the customs officials.
However, by & large, the boys in Singapore might look good, but most are unavailable to us.