To get you started:
**broken link removed**
SparkFun also has ALL the parts you need hiding on their website...maybe even a sample circuit...(but since you're in INdonesia you will probably have to find equivelant parts, but it gives you an idea of what you need).
Basically it comes down to this:
1. You need at least one thermocouple wire.
2. For every thermocouple, you need a cold-junction compensation IC to convert the thermocouple reading so that an MCU can use it.
3. You need an MCU to read the thermocouple reading.
4. And you need to be able to turn the oven on and off. You can use a relay or TRIAC. Either one will work. Relays are either on or off and simple to use. Triacs need some support circuitry like isolation circuitry (for saftey), but allow you to let varying power to the oven to have better control of the heating element.
-make sure your TRIAC or relay can handle the voltage and current your oven will pull and make sure your relay and TRIAC has the right voltage/current requirements so you can run drive it with your MCU (or a power transistor being driven by your MCU).
You can either open up the oven and hook the TRIAC or relay right between the main AC line and the heating element- this is dangerous if you do it wrong. You can stick the TRIAC or relay between the oven and the power outlet. When you do this method you turn the oven temperature to max so it will always stay on when the oven power is connected (ovens can reach temperatures a few times higher than what soldering needs so the thermostat should never kick in).
The rest is coding so that the MCU can control the relay/TRIAC based on the temperature being read.
Saftey first in this project- don't electrocute yourself by doing it wrong.