Please assist to recommend a lens filter which suit to take photo at beach side. For the purpose of making the sky bcome dark blue. Is that Polarising Lens Filter suitable for this application. Currently im using Nex 5 with SELP1650 lens. The lens filter size should be 40.5mm right? Please recommend a shop or seller. Thanks for your help.

Yes, correct, polarizing filter serves this purpose.
Note that there are plenty of fake filters around, so buy from reputable seller.

u can ask from foto shangri-la at mid valley. they selling original for various brand of filters. may expensive a bit compare with outside

how about from this website?

www.shashinki.com

I found H&Y MRC CPL 40.5mm Filter from shashinki. Is that H&Y is a good choice?

if you got budget, go for lee filters, hoya, B&W. Try to get the largest filter and get an adapter for it.

Any shop do sell fakes. Not easy to know also. Expensive means original? I doubt so.

my budget around 150+, H&Y not a good choice? Anyone use before? I stay penang, which shop got sell original Hoya

Other than a circular polariser, you might need a graduated ND filter - where the top part of the filter is darker than the bottom part of the filter.