I don't think you can get a mechanical keyboard for RM50, even the China ones. But if below RM200, off the top of my head I can recall the following: Magicforce 68, Anne Pro, Ajazz AK33, Fuhlen. There may be others but I can't remember them now.
I'm no expert but it depends if you want 'gamery' keyboards or more basic ones. The former would include Razer, Corsair, CM, Steelseries, etc. I'm not too familiar with the later, but if the more basic ones without RGB/backlit maybe can take a look at the Ducky Zero TKL non backlit & also IKBC TKL. CM Storm also have a few models which falls between the gamer crowd & the more serious work crowd..e.g. the Quickfire TK & Trigger Z.