When i arrive in Thailand soon, I am planning to buy a New Yamaha Spark 135i
I see they are listed on this site at 52500 baht
Is this price fixed, can a lower price be negotiated for cash.
What sort of deal could i expect for cash?
What would it cost for rego etc.?

Any advice much appreciated.
thanks
Matty...

The prices you can find on our motorcycle price list are suggested retail prices, it's possible that Yamaha dealer sell the bike for another price.

For discounts on small engine motorcycles, dealers often offer you accessories... free jacket, helmet, bag, etc...

Prices by Thai motorcycle dealer are always on the road prices, and a basic 1-year insurance is included (needed by Thai law) – this insurance doesn't cover much, it's recommended to ask how much an First Class insurance cost.

I will be bringing my own helmet , jacket and disc lock.
What other accessories would you recommend? An would aftermarket performance muffler be worth while?

An aftermarket exhaust system will increase performance, but don't expect too much from it. Still it's worth the money, all is it alone for the sound.

As you in the market of buying a new motorcycle, you maybe want to look at this website I found Buying a New Motorcycle