Step to reproduced :-

1 Thai text in double quote.
 1.1 Open OpenOffice.org Basic IDE.
 1.2 Type “สวัสดี Hello” (with the quotes).
 1.3 You'll see overlapped text.
2 Thai text without double quote.
 2.1 Open OpenOffice.org Basic IDE.
 2.2 Type สวัสดี Hello”(i.e. without double quote)
 2.3 For Windows XP you'll see some box characters.
 2.4 For Windows Vista you'll see some box characters and the screen will blank
after some keystrokes.