Hi. Documentation states:

new ( HOST, OPTIONS )
...
You can also specify a URI, such as 'ldaps://127.0.0.1:666' or 'ldapi://%2fvar%2flib%2fldap_sock'. Note that '%2f's in the LDAPI socket path will be translated into '/'. This is to support LDAP query options like base, search etc. although the query part of the URI will be ignored in this context. If port was not specified in the URI, the default is either 389 or 636 for 'LDAP' and 'LDAPS' schemes respectively.

I tested this with tcpdump. I tried both prepending ldaps:// and appending :636, but neither is respected. It sends unencrypted traffic over the default port (389).

The only way to change the behaviour is with options.