Question, are tenants or owners allowed to go up to the roof of a condominium

for leisure activities at all hours of the day and night ?

We have few people who insist on going up to roof using one or our 2 set of the

emergency stairs to "view the scenery" despite repeated warning that the roof is off limit,

We, the management, do concern for the safety of those people as well as the security issue,

The roof is not considered a common area of the building to congregate on, and should be off limit for anyone unless they are going there to do necessary repairs of chattels on the roof. An official sign in Thai and English should be installed saying that the roof is off limits, and then if people insist to go there, there, this should be enforced (but this is Thailand) with a large fine. The other alternative is installing locks on the roof exit which only management and maintenance people have, but leaving the doors unlocked could pose a hazard incase of fire.

The other alternative is installing locks on the roof exit which only management and maintenance people have, but leaving the doors unlocked could pose a hazard incase of fire.

I think you meant locked. But the door to the roof can be left locked and a key to the lock can be sealed into a metal box with glass which can be broken in case of fire.