In Singapore its illegal to own a radio scanner. If I recall correctly, there is a fine of $10,000 and up to three years in prison, or both.
It's more likely that any forwarding service will refuse to ship it to your Singapore address. However, if they do, it'll probably be impounded at Customs, and won't be returned to the sender. Someone else more knowledgeable can probably advise if you may also be charged for attempting to import an illegal item.
From Telecommunications Act (CHAPTER 323):
Part IV OFFENCES AND PENALTIES
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Prohibitions in respect of telecommunication and radio- communication equipment 34.
—(1) No person shall —
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(b)possess any radio-communication equipment, except and in accordance with a licence granted under section 5 or any regulations made under this Act.
(2) Any person who contravenes or fails to comply with subsection (1) shall be guilty of an offence.
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General penalties
65. Any person guilty of an offence under this Act or any regulations made thereunder for which no penalty is expressly provided shall, in addition to the forfeiture of any article seized, be liable on conviction to a fine not exceeding $10,000 or to imprisonment for a term not exceeding 3 years or to both.
If you didn't already know, all Police, SCDF, and Ambulances, have switched over to the TETRA Trunked Radio System, which is encrypted, and impossible to listen into. Similarly, mobile phones here use GSM, which is also encrypted so it's not possible to listen in to them either.