In a nutshell yes you can daytrade, certainly to Hong Kong, but due to transoceanic latency some speed based scalping strategies in US products may not be viable.
Just a few days ago there was obviously some upgrading done and I now have a virtually packet loss free connection. Quality seems to vary depending on where you are in each ISP's capacity vs subscriber adds cycle. At the end just before an upgrade is forced by having too many subscribers for the existing bandwidth and infrastructure you have a bad connection and then after each upgrade you have a good one for a while. Numbers have gone from 10,000 to 250,000 users in 2 years with upgrades lagging. Bottom line is that this has meant there are periods when day trading has been non viable and/or strategies must be adapted.
The physical ADSL link is generally stable. The major issue is their ISP software capabilities and reliability and overseas bandwidth as this is where they try to save money. I was paying USD75/month for unlimited hours with Ji-Net for a stated 512K and tested actual 300K. I switched from TRUE as the quality deteriorated and I was paying Bt44 hour for excess usage. Ji-Net was absolutely fine for a while then it started to deteriorate to the point of unuseability, so I switched back to TRUE on a new unlimited package of 2.5MB stated, actual 300k (more now after upgrade).
At the time of writing I have a reliable connection that does not disconnect or show high packet loss. 3 weeks ago this as not the case and I had several disconnects in a day. Now, after the first disconnect I stop trading, but you don't know when it's coming and this can force you to adapt how you trade as can latency. e.g. the 'dammed if you do and dammed if you don't' issue of using hard stops in a market rife with stop running in case you have an outage, or using limit or Stop limit orders in advance to prevent you from hitting prices that no longer exist or being last in line (read: filled at whipsaw point) with a market order. I have frequently closed out trades ahead of target when I have an advance warning of trouble from Pingplotter or DUmeter. Frequently these are false alarms but HSI can reverse very fast on some days.
I miss a lot of trades through being too slow in some ways but it's difficult to isolate reaction times, etc from latency etc. I have become leery of using market orders. Right now market orders are neo viable to HK as latency is around 300 ms to HK (was around 700ms recently), but add transocean times for US markets. The slippage is around 3 ticks HSI which is fine for a big move but I generally anticipate with market or stop limit orders. On breakouts/downs in HSI if it blew through a stop limit believe me, there are time when you would not have wanted the fill you would have got ATM.
Another reason I use limits is that it seems the credit verification takes place in the time it takes for the market to trade to my price. Note that the biggest delay in market orders is probably the eternal wait while broker server verifies your available margin not internet latency.
Bottom line is that when everything is working fine you can day trade and can neo scalp but there are almost certainly some speed based things that might not work due to latency i.e. the price you are seeing was already hit in Chicago by someone with a 700ms reaction time.
