do i need to bring protection gear to south asia?
 

If you can carry it I think I would. Using unfamiliar gear is just another thing with which to contend in a strange environment.

I did in Cambodia:
2008.12 Cambodia - a set on Flickr

You can rent all the gear though (probably not everywhere). You'll have to choose between the comforts of traveling light or a helmet with no sweat but yours... .

at least take your own helmet
 

I would if were you, I hired a bike on several occasions recently and did not feel particularly safe in the poor quality, ill fitting helmets supplied. A pair of summer gloves and a lightweight jacket with a bit of armour would not go amiss either, I never saw any available in either Thailand, Laos, Cambodia or Vietnam, but did see quite a bit of gravel rash on other motorcyclists.
Take care and have fun

" Do I need to bring my own helment, protection armor ..."

Yes.

I would bring at least my helmet and a back protector.

I´ve ridden in Asia without the rest of the gear, but you´ll need to understand that if you go down, you may be in a bad shape, at least your holiday will easily be ruined - and you possibly would not be that way, if you had worn all your gear.

Sometimes I´ve also used a motocross armored ´shirt´, and knee protectors under my pants, and riding shoes and gloves. They are a bit hot in that climate, especially when you stop, but considering the outcome if you crash, I´d still recommend those for a 1st-timer. The shoes are a pain to carry around on your luggage, though.

Some proper gear is available in big cities, but I wouldnt waste my holiday trying to find them (and if you´re large size, may be tough to find anything that fits!)

i would take it if i were you .in some places it can cost as much for gear as it is for a bike.also most of the people in asia are of a smaller size so you might not always find a good fit .