If you win, the tenant will pay all the cost plus double the rental owned. You cannot just chain the door. Before any judgment is made by the court, they have the right to stay in the house.
The problem is that in some cases, the landlord is really in the wrong end such as not repairing, maintaining the place, the tenant doesn't want to pay rental. Although the tenants should not make non payment under any circumstances, if you chain the house and the tenants sue you, you may in the loosing end.
You have to go through proper way to solve the problem. Singapore has very good law implemented to protect either parties. There is no worry if you are in the right end.