What Godzilla said was true about the guide fees. The guide fees are regulated and capped by the authority. To make it worse, tipping is discouraged even before travelers touch down here. While I wont disclose the guide fees here, it is certainly not sufficient for a guide to survive on the fixed salary alone.
I believe tipping is a sign of appreciation after a good service. While the authority says it discourages tipping, i dont think the law suggests it is illegal or criminal to tip. Otherwise, we can see several tourist in changi prison arrested for tipping against the mandate.
Hehe.....trust me local tour guides gets a lot of SHI* from different tourist and yes, they do not earn as a lot from it. 90% of the tour guide in Singapore has no fixed salary. Most of them are freelancer.
Authority knows nuts about how much a tour guide earns. It's not illegal or criminally wrong to tip a tour guide knowing how much they really earn.