Spass rejected, Is it because Indonesian?

I don't think your country origin will be an issue for your pass rejection rather I see the mismatch of salaried offer to you in compare to market standard. A graduate with 5yrs relevant experience in your domain was offered $3,600 per month is way below to market standard. Ideal salary should be around $5,000 plus.

I see. Thank you for your replied. I thought because EP got rejected, I tried to applied Spass because lower standard. Actually, I have Philipines friends who got his spass last month, he has more experience than me(about 30 years old).

Use SAT to check which pass u qualified for.

I am qualified for Spass

Each application is reviewed at MoM in case by case basis. So, I would read it differently against your colleague who had 30 years of experiences. You can use SAT to see your eligibility but at the end of the day it's the officer who is reviewing your case and what he thinks about your case. Best of luck.

No, I mean he is 30 years old, not 30 years experience, it means about 7 years exp. Is it worthed to appeal by giving them support proof from CEO,CTO, manager? If the case is because my salary should be higher, then there is nothing to appeal

Correct, I read it wrongly. But no point writing someone's age in future, rather mention his years of experiences.

There is nothing wrong to appeal where your employer can provide an evidence that they support your employment in their organisation and furthermore try to furnish a letter stating that how your job scope will help company to grow in its clients deliverables and how you are a valued employee for the organisation. Meantime check with the HR if they have foreign quota to hire a foreigner as sometime what happens that if a company completed its foreign quota then MoM will reject the application. Good luck.

Okay, thanks for your information, it's really helpful.

As a Southeast Asian Chinese, you are of the preferred ethnicity for Singapore work passes.
But like Surya said, you need to earn more. They don't accept foreigners undercutting the local wage market.