It may or may not work depending on several factors. Your VPN client may require ports to be opened on the network that wherever you are visiting may not have opened by default. You will be unable to access VPN at all if this is the case. As you already suspect, there may be a bandwidth issue wherever you visit. You have a dedicated 2Mbps link and wherever you visit may not have a dedicated link for your use so you may be sharing with a number of other users and contending for access. The other issue with shared access may be quality of service (QOS) issues for your VOIP application. It is also likely that there will be high latency from Bangkok which creates issues like echo, lost packets, etc for VOIP.