There is absolutely no context in one sentence. So, how can we tell the context where there is none??
Because Vietnamese doesn't make use of it if not necessary. In fact, it's mandatory in English, but really is superfluous for understanding the meaning.
Watching the clock has a deeper meaning in english refering to 'keeping an eye on the time'. The context of this phrase is elusive so i think "I watch the clock should be accepted
I have had LOTS of sentences that translate "xem" to "see". Rather confusing.