I try to create a global category and then i found that post.
Andrea_r said: Use wpmu-new-blog-default to solved this.
Overall is ok - but when i use my language "Thai language".
After I saved a form, all of input is blank.
So now i was solved this, i try to check table
wp_sitemeta and i found a collection is not 'utf8_unicode_ci' then i changed it.