I found Singapore to be a little challenging also on my recent vacation.
I found eating at home easiest, and then while out and about fruit salad was a common option with a soy latte to keep my going. The restaurant Boomerang looked after me and they were familiar with gluten free, but many places had not heard of it. However, I share my amazing experience at one venue.
I sent an email to firstname.lastname@example.org and requested a reservation and advice re gluten free options.Contacting them in advance is a good idea.
I would highly recommend dining here as the buffet and alacarte menu looked magnificent, and we enjoyed our food a lot. I enjoyed
smoked salmon with young masculine and lemon dressing for entree
pan seared chicken breast with young asparagus olive crushed potatoes and light jus
seasonal fruit platter with sorbet (lime, strawberry, lychee) with other sorbet flabours
there was another magnificent main option
we booked at 6.30, sat outside which we liked; and perhaps arriving early meant less busy and better service, but our waiter was exceptional, provided a very personal service, on first name basis, and expertly assisted with choosing meals - and the chef asked us did our meals meet our expectations. they exceeded mine, magnificent food prepared by chef fully aware of Coeliac disease and gluten free.
The hotel environment and service looked amazing. If you need gluten free dining, and fantastic food and service is to your liking, then choose MELT. I found it on open table via a google search. I hope this helps