Something occurred to me after posting the last blog entry. It's important to know when to use "English English" and when to use "Thai English."
Personally, I tend to err on the side of wanting to sound too much like a Thai. But that's not always the best strategy. Particularly in educated company, knowing when to bust out your native accent is a useful skill.
In general, though, my comments on this topic relate to those English words which have become part of the greater Thai lexicon.
But say you were talking with someone about Bill Clinton. You have several options: using the extreme Thai pronuncation [บิน คินตั้น], or the slightly more authentic but still Thai-sounding [บิว คลินตั้น], or you can just say it like you would in English. Know your audience, and their background with respect to English. Make sure they'll understand what you're saying.
Also know what effect you want to have. If you want solidarity, mimic the pronunciation of the person you're conversing with. If you want to be exemplary or corrective, model the "proper" pronunciation. If you're not sure, hover somewhere in between.
Context is key.