since we dont need anti freeze here, what do i add to the water in the radiator?

anti freeze is this best coolant even in climates such as Saudi Arabia where it can reach over 52 C. It is just not for freezing this is a misconception.

If you look in the shops for Coolant, can be found lots of places including Carefour.

Anti-freeze has anti corrosion stuff in it, a must for any engine with aluminium parts, head etc..

Most PTT stations sell the stuff. 178B for 1L bottle. Failing that, most large supermarkets like Tesco, BigC, Homemart will probably carry the stuff in their auto sections.

In Thai it is called: น้ำยารักษาหม้อน้ำ - "num ya ruk-sah mor num" or many brands have "Radiator Coolant" printed in English as well.

thanks guys and especially soundman for the very helpful thai translation