Hi Spuluka,
I did some troubleshoot today. Here's the setup:
From ASA5506 I managed to ping its connected interface to SSG140 even the client that is connected to 100.100.2.0 subnet.
From SSG140:
1. Ping 10.151.1.251 from source ethernet 0/2 and 0/0 both are reacheable.
2. Ping 192.168.2.1 from source ethernet 0/2 and 0/0 both are failed.
SSG140 has route configured, by right it should be working fine. My setup goal is to get network (100.100.2.0) to reach 150.150.0.0 network behind the ASA5506. But I'm stuck at SSG140 that was unable to reach ASA5506 outside network. Appreciate if you could advise. Thank you. Here I attached the configuration files.