Models and specimens of inventions are normally not required in patent applications. You are required to furnish a patent specification containing a set of description, a claim(s), a drawing(s) (if any) of the invention and sequence listing(s) (if any). Any examination would be based on the patent specification.  However, if your invention involves the use of micro-organisms, you would be required to deposit a sample of that micro-organisms. Singapore is a party to the Budapest Treaty (Treaty on the International Recognition of the Deposit of Micro-organisms for the purposes of Patent Procedure done at Budapest in 1977). You can therefore deposit a sample of the micro-organisms with any one of the international depository authorities as stated under the Budapest Treaty. For more details, please refer to the WIPO website.