Hi,
Is your player free to move and you want to check if he's walking on the right tile, or do you want to constraint your user so that's it's impossible for the player to actually be on a tile?
Typically, I would create a box collider that is sitting on the tile so that is it's a trigger I know the player is on it, and if I set it to a collider ( unchecking "is trigger") then the collider itself will prevent the player to move on this tile.
the question also is what type of character are you using? is it physics based?
bye,
Jean