Is your Google account in Thai when you log in? You should be able to change it for all Google services (on that user only) by going to this link.
If you still find that things such as Google Drive are in the wrong language, you can make changes directly in that service.
Click here to change Google Drive (docs) to English.
If that link doesn’t work for you, log in as normal and simply go to the gear on the right side (under your user name). Click the first link in the third section and then select English. Save your settings (left button) and you are done.
Here’s what it looks like (no audio):
http://youtu.be/yMEydYCNxfI
Forcing English Language on Forms
When you want to send the link to people to fill in your form, you click on the button for Send form. This gives you a long URL like this.
https://docs.google.com/forms/d/e/sH34...mWtL/viewform
If you want to be sure that the respondents see the directions in English (or some other language), you can force the language. (Note, this will not change the language of your questions, just the web page around your questions.
All you have to do is add “?hl=en” (without quotes) to the end of the URL to force the language. Here is a list of Google language codes that you can use. Here is an example.
https://docs.google.com/forms/d/e/sH34...mWtL/viewform?hl=en