How doI say this?

Dont know the context.

Something like this, ฉวยโอกาส?

Or, perhaps

เอาเปรียบ ?

Dont know the context.

Something like this, ฉวยโอกาส?

I think ฉวยโอกาส is more like "seize the opportunity to ..".

เอารัดเอาเปรียบ

I am not sure what the OP is asking for. The phrase "to take advantage of" has two meanings: 1. to seize an opportunity presented (the non-pejorative meaning) and 2. to use someone to their disadvantage (the pejorative meaning)..

If the OP is asking about meaning 1, the answer is ถือโอกาศ or ฉวยโอกาส as AyG and rgs2001uk said; if the meaning is that in 2, the answer is "เอารัดเอาเปรียบ" or "เอาเปรียบ" as Neeranam said.

Edited December 15, 201312 yr by DavidHouston