I have a big problem with regards to my toilet bowl (siphon jet toilet).. because if it is unused still it will automatically drain the water out to a small hole (jet)...

This is caused by a blocked vent. When you drain or flush it sets up a suction. This is relieved by the vents but if the vent's blocked the system will attempt to vent through a trap. In this case your toilet. The suction's what's pulling the water out of your bowl.
The solution would be to snake the bathroom lavatory roof vent.
Put out enough snake to reach the base and 20 feet more, Good luck, Tom