As I understand it, there is no R/L distinctions in Chinese, Japanese, or
Korean.
That is, English has minimal pairs of words that differ in meaning because
of the R/L distinction (like "rice" and "lice"), but there are no such
minimal pairs in Chinese, Japanese, or Korean.
And in Japanese and Korean, there are no instances in which the meaning of a
word depends on a pronunciation that differs only in si/shi (as in "sit" and
"shit" in English).
Question: Is there a si/shi distinction in Chinese?
The answer seems to be Yes. Looking at the Pinyin
romanizations of シ words in Chinese, we find
四 si
市 shi
But the sound romanized by "shi" in Chinese is not exactly the "shi" sound
in English. Instead, the Chinese sound romanized by "shi" involves folding
the back of the tongue in a way that is not done with the English-language
sound "shi". So will an English-language "shi" sound be heard as a Chinese
"si", or as a Chinese "shi"?