I find internet in thailand Ok for trading unless one extreemly scalping. Trading from internet cafe or in-room DSL from hotel proves nothing as to reliability and speed for any location in the world
If trading from hotels and internet cafes in thailand, you should keep in mind these points:
1-Internet cafes not necessarily using fastest connection available, depands per # of PCs they are using, let say they have 10 PCs, and in order to keep the cost down, they might go for slower package 1-2MB only (generaly people are not much bothered with high speed while on vacation, unless one wants to trade)
2-You are connected through a router, the port that you are using might lose you any moment , while others on same service still have no problems (happened to me many times) either had to change my room for this (grand president in Bangkok) or ask the owner to change the port (sunnet internet and guesthouse in phuket)
3- Afaik highest speed you get in Bangkok is 4MB while phuket is 2MB only, meanwhile internet is lot cheaper in bangkok with many service providers, so you should afford to have another DSL as backup.
4- Internet really get slow every morning (US and European market still closed) when Thai exchange SET and general business start
5-You should have a broker that can place "native" stop-loss with every order, incase connection is lost