Is this possible (and realistic)?

Arrive into SIN at 10:30p.
Plan to stay in transit hotel overnight.
Outbound does not leave till 1:15p.

I'd like to do the morning free city tour. Can I get up from the overnight in the transit hotel and go to sign up for the city tour? According to the "requirements", I'll be in transit, I'll have enough time before my departure...

Having never been to SIN (or Singapore), I welcome any/all suggestions.