difference in pay between NY and Asia

pretty much the same. Actually HK is higher, as they provide housing allowance and the tax is lower.

Any idea about the numbers in Singapore??

HK is higher? Brilliant.

Bonuses are significantly lower in London & HK as compared to NY, at least for associate positions.

Between HK and NY, the total comp is about the same. Banana Milkshake is correct in that bonuses are lower in HK (don't know about London), but that is because bankers in HK receive a housing allowance. Essentially, the housing allowance acts like a guaranteed bonus. In other words, NY base + NY bonus = HK base + HK bonus + HK Housing Allowance.

On the tax issue, if you are a US citizen, it doesn't matter where you are, you're going to pay the same taxes. If you're not a US citizen, then you will save a significant amount on taxes by working in HK instead of the US.

HK has higher base and bonuses based on personal and anecdotal evidence. 1st year analysts at a place with good deal flow can make nearly USD200k, and they pay 15-17% tax on that. In other words, they make over twice what their NY counterparts make post tax.

Not exclusively. The usual non-bulge bracket suspects like Blackstone have just as much an edge over there as they do in New York.