Balcony Safety - Child Locks

Trying to find & fit a basic low tech safety/child lock to fit to the sliding door onto the balcony - anyone had any experience, or can recommend tradesman/ handyman to do the job? We are in BKK Charoenakon Rd area next to the river.

Condo staff seem puzzled by the request - our condo building is recent with fairly good specs (by Thai standards)but the balcony design is poor in terms of safety.

Edited October 10, 201312 yr by Taantip68