I am posing my first thread.
I am looking for any help that you might be able to give me. Where to start

My father born 25/2/1923 John beverley Miller merchant navy alien registration 9518404
Which I got from United States coast guard identification card.
I have found he was on ship Tekoa which arrived October 15 1942 into New York
And on same ship for another voyage arriving 24 or 25 Feb 1943.
I am trying to find his ships and passages before after thipose trips.
I believe he skipped ship and was in Singapore and had a child to a women there. I have no proof of the just family folklore.
If anyone can give me any help where to look for records that might help, I would be grateful.
The only records I have are those from New York alien arrivals and 2 card records of those 2 trips which I am trying to understand.

Regards Russell Miller