When I sailed with China Nav in the 1950s, deck passengers were the norm on all their intra-Asian trades. That would have been the same with all the other companies trading out East. But I am not sure whether the likes of Blue Funnel or Ben Line would have taken any from say Hong Kong to Singapore.
I have now come across a passenger list of the Lycaon that carried deck passengers FROM Liverpool to Hong Kong in 1923.
Would anyone be able to confirm that was common?