Last night I follow the instruction of replacing Helvetica fonts from the web site:
What I did are:
1. copy Nook font from system/fonts/ folder to my PC
2. rename all five Helveticaxxxxx fonts to _Helveticaxxxxx, except Helvetica_medium and Helvetica_medium_italic which I cannot find any suitable replacement
3. copy five BrowalliaNew fonts (have Thai characters) to the folder on my PC
4. rename BrowalliaNew to Helveticaxxxxx. Also create Helvetica_r by copying normal BrowalliaNew font
5. replace my Nook system/fonts folder with the one on my PC
6. reboot my Nook
I did not see any change on interface fonts. Thai author name still display as alien text. All interfaces fonts look the same for My Library, My Book, Daily. Webpage rendered by Nookbrowser still display Thai as alien text, e.g. m.gmail.com, m.yahoo.com, twitter.com.
I'm not sure what to do next to make it work.