Maybe you can try the following method which I learnt from a parenting class few years ago.
(1) When the baby cries, let him cry for about 5 minutes (don't stand by his cot), you need to be out of his sight.
(2) If the baby still crying after 5 minutes, then pick him up and pat him for a few seconds but no eye contact with the baby and don't talk to the baby at all. , then put him down again.
(3)If he cries again, then repeat the same procedure.
After few times...he might fall back to sleep. (do remember no eye contact and talking at all)
If the next day, the baby cries again, then repeat the above procedure but with 10 minutes intervals.
Then use 15 minutes intervals, then maybe even up to 30 minutes intervals gradually . Usually the baby stops crying in the 15 minutes intervals according to researches. This applied to my first kid.