เคยเห็นเค้าใช้ตัวนี้นะครับ
http://wordpress.org/plugins/wp-smf-a-simplemachines-bridge/
wordpress กับ SMF
** Backup ข้อมูลไว้ก่อนนะครับผมก็ไม่เคยใช้
This plugin hasn't been updated in over 2 years. It may no longer be maintained or supported and may have compatibility issues when used with more recent versions of WordPress.
เพิ่มเติม
http://www.nampheung.com/4684/%E0%B8%95%E0%B8%B4%E0%B8%94%E0%B8%95%E0%B8%B1%E0%B9%89%E0%B8%87%E0%B9%80%E0%B8%A7%E0%B9%87%E0%B8%9A%E0%B8%9A%E0%B8%AD%E0%B8%A3%E0%B9%8C%E0%B8%94-wordpress.html