This time round it's not Indonesia, it's Malaysia. The fires are still raging on, so expect the haze to continue on for at least a few more days.
The most hazardous PM2.5 (ie. 2.5 picometers particulates) reading from this haze is very bad, it's as harmful as cigarette smoke, hence the similar choking sensation. Long term exposure will increase risk of cancers of the respiratory system.
From the Indonesia haze episodes in the last couple of years, every Singaporean household should already have invested in at least 1 decent air purifier. If you've not yet done so, you better do so soon. You can expect haze episodes, whether from Malaysia or Indonesia, to be an ongoing problem every year or so.
A note of caution, if you buy Air Purifiers from Amazon.com, note that these are meant to be used in USA (where a different household voltage of 120V is used, instead of Singapore's 240V). You'll need to buy either a transformer or a converter (technical physics difference, but both serve a similar purpose) with at least 300W capacity, required to transform/convert Singapore's 240V into USA's 120V before the air purifiers can operate.
http://www.amazon.com/gp/product/B00007E7RY/
http://www.amazon.com/gp/product/B00005QELT/