Upgrading Drupal 4.6.x directly to Drupal 6.12

I have upgraded KhmerOS website, using drupal 4.6.x, directly to the latest version Drupal 6.12 successfully.

But the problem is Khmer Unicode is still not displaying yet. I am getting stuck with Khmer Unicode characters , unknown characters like "សូម​ស្វាគមន៍​មក​កានáŸ" :(.

Instruction: http://drupal.org/node/388994

ChanHan,