In the Foreign Policy article you are quoting: "Although China’s official 2012 defense budget is $106 billion, ...the Pentagon places China’s total military spending at somewhere between $120 and $180 billion."

So we take the number in the middle ($150 billion) and assume it's always a 50% undercut (extremely inaccurate estimate), this will put China's 2016 budget to 1.92%*1.5=2.88%, still lower than Singapore's.