Siamese cat frequently fighting in neighbourhood

Question
I do hope you are able to help with my 2 year old male Siamese cat, Mika.

Mika is a wonderful cat who, like all Siamese is intelligent, sociable and requires human interaction.  We got him from a breder and he was neutered as a kitten.

Mika lives with our other cat 3 year old Willow and they do get along most of the time.  He can be territorial in the house with her and displays jealous tendencies with myself and my partner especially as I am not there most of the week.

The main concerns we have with Mika is that when he goes out he can be out for a long time sometimes coming back early hours of the morning with puncture marks where he has been fighting with I presume another cat. These tend to be on his head and his sides. He has had numerous abscesses on his head which we had treated by our vet.  We don't have a cat flap and are concerning if he has more access during the day would this reduce the length of time he disappears thus injuries to him?  However I simply am unsure if this would work.  

Both of us work during the day and I am with them on a weekend.

I'm very concerned about him as I don't know where he goes and why he's being so territorial.  This has gradually got worse over the past 6 months.

Any ideas?

Answer
Michelle,

The only way I know to prevent the fighting is to make him into an indoor cat.  This can be a long process.  You or your partner can leash train him (leash and harness) and let him get his wanderlust out of his system by having regular walks (whereby he will walk you).

Leash training is relatively easy and can often satisfy the urge to be out of doors.

Outdoor cats who are indoors tend to be excellent escape artists, so you would have to be very vigilant.

Please let me know what you think.

Best regards... Norm.