Dear Liyanning,
As per our discussion over the phone just now that I have discussed this with Khun Kittipath. The solution for not registering this store as a branch is a short term solution to avoid the penalty for tax bureau ( which the given deadline is today). For longer term solution, if there is a need for registering the branch, or you want to look for a new place with bigger space, this option for registering is still open.