Multi-Select result in form is not submitted, why?

I have a form, with some value such as name/description belong to one
table eg. tbl_1, they are obviously got submited, I have checked all
contents in @param.

However, I also have 2 multi-selection list in the form, the selected
value does not show up at all in the @param dump. These two list are not
directly related to the tbl_1, but tbl_2 and tbl_3, which both has n to
1 relationship with tbl_1.

When I check the @param in the action in controller, the multi-lists are
not even mentioned.

I am very new on RoR, I probably missed something obvious…

Please help!

Thanks for any help!