In which bases we should consider the item as capex or opex . e.g Laptop costs 2000 SR Capex or Opex?

Buying anything which builds an physical asset should fall in Capex.So answer is CAPEX

As per the internal capex policy for each company , and also the maintained minimum limit for considering the item as capex or opex , so it is clearly depends on the capex internal policy anbd also the nature of the item itself .

If we take your example: Laptop. You need to look at the laptop usage. If it is part of a service rendered ( maintenance...) it is Opex. If it is a tool to connect with a network for ex ( NW management), Then it is Capex. 

Capex, depending on company's internal policy.  The asset has to be clearly marked and Added to the respective emploee's name to prempt any misuse.  Even though the cost may appear insignificant, it brings in a sense of esponsibility.