Siamese adoptee crying at night

I recently bit the bullet and adopted a cat! While I’ve had cats my entire life, I never had the resources to offer a kitty a good home in my adult life – until now. I ended up choosing a lovely, male, seal point Siamese who had been at the shelter for over two months! He’s ten years old, a bit chunky, and incredibly fond of being pet. He’s also, as most Siamese are, quite talkative. Which is fine during the day, I love our little chats. But at night he walks through the house meowing (and yowling) plaintively, and I don’t know what to do. He doesn't cry the whole  night. He spends some time in my bed sleeping, and then some time in his  bed sleeping, but then at other times he's crying.

He was adopted about a week ago, and while some of this could be stress-related, he was very relaxed when I brought him home. He lounged around in a separate room for a few days, but he started getting antsy so I introduced him to the rest of the apartment. He proceeded to lounge around in the rest of the apartment, baring his belly, begging for pets, generally being adorable.

I live in a townhouse set up, with paper thin adjoining walls, and I’m worried my neighbors are going to complain. If they do, I’ll be asked by the apartment complex to give him up. I can’t even consider the possibility. He was at the shelter for so long, has a terrible cold and conjunctivitis from there…

I also work full time and I worry that he’s lonely and crying during the day too… and despite my longing to keep him I can’t possibly force him to endure that if it’s not just a phase.

Is there any hope that he will quite down eventually? Is there something I can do to help him along?

P.S. The folks at the shelter called him an “undemanding but affectionate” Siamese – they had him listed as a good cat for first time owners because he is apparently incredibly low maintenance. I asked them specifically if he would be okay being owned by a full time worker, and they said he would. But I’m not so sure now. :/

 I once fostered a girl who was taken from a breeder.  She was a Tonkinese, so, a Burmese and Siamese mix.  She was so affectionate but when I brought her home she just howled!  I couldn't believe it.  I took her to be spayed and she howled there too!  Then, after a while she realised she was safe and had a home and she just stopped.  Trouble is, I was just a foster.. when we found a good home for her, same thing.  But I'd warned them and after some time she quietened down.

In those days I didn't know about Feliway.. the pheromone diffusers (although I prefer the spray).. which can work well. 

I don't suppose another cat is feasible if she doesn't settle?  But honestly, I think she should.  Talk to the shelter people and see if they know whether she did it when she arrived there.

I definitely think that it is his new environment.  He's not really used to your schedule and his world is way different than it used to be.  My Tonk has gone through periods of night howling at different times during her long life and was usually remedied with a night time play session and lots of petting before bed.  It could last several weeks so bear with him.  It is not permanent behavior and definitely stress related.  That breed has the ability to make their feelings known.