The boy said in a Facebook post that the day he leaves Singapore, he is going to take "a big big revenge" and "spit everywhere" and "plant bombs on Marina Bay Sands", Xinhua quoted the Straits Times as saying.
The post also contained an expletive and was critical of Singapore, the report said.
Police said they were in touch with the school the student listed on his Facebook page.
The boy, who cannot be named as he is a minor, is believed to have posted the threat last week.
The offence is punishable with a fine of 100,000 Singapore dollars ($80,000) or imprisonment for a term not exceeding five years, or both.