I recently was in the same area and happened on approaching screws from the south (TMO/RSRDC) after a long stretch of finding nothing. Headed north out of Singapore were 6 escorts (all DDs) and three columns of 5 merchants each. A happy hunting ground, to say the least. My only regret was being in a Porpoise at the time
Date was early 42 (I was still based in Java).