It is one of the Eleotridae family (so are Butis butis), this one looks like it could be a Northern Mud gudgeon (Ophiocara porocephala). They are often found in the same waters as Butis. They ate FW to brackish and get about 13" long. Not super aggro but will eat fish that it can get in their mouths, up to about 1/2 their length.