I know very little about tailoring in Singapore, but what I do know is that it is incredibly expensive and I have friends in Singapore that fly to Hong Kong just to save on tailoring costs (actually ends up being cheaper taking into account flights etc). If you have options in getting your tailoring done elsewhere I would explore them. 

try Maharaja’s Custom Tailors Marina Mandarin Singapore

or

the chain of boutique tailors, Marcella, in various locations.

Ethanmen would be a great choice. They do not make sloppy or cardboard-like collars and cuffs like many of the local tailors which I detest.

CYC The Custom Shop is by far the most famous and reputable one. But it is also at Raffles Hotel. Which also means it is about $120 - $180 but well worth the money. Quality fabrics and exquisite details. I had most of my work shirts and shirts for wedding done there. There's also Next Apparel in Bedok. Price about $80 - 120.

Mohan's Custom Tailors is the best I have found. They have made the best fitting shirts I have had with great material for SGD$80 if you buy a minimum of 6 shirts.