S pass approved. But i will not enter SG to work as an Spass

You can only get an S-Pass with a minimum salary of S$2300/month. The employer is not allowed to pay you less (especially if they declared a higher pay to get the visa for you!).
But if this was two years ago, the associated IPA is certainly long expired.
This will count as a negative point for any of your future work pass applications, but should not have an impact on a tourist visa - unless the employer filed a complaint against you (e.g. if you absconded the job without proper termination, or something else happened that you didn't tell us).

S pass just got approved this month. The reason that i don't wanna work and comeback there is because they will just give me a monthly salary of $1200sgd. But they declared in MOM that they'll pay me for my salary $2700sgd.

This is illegal!
You should report this to MoM in order to prevent the company from cheating others in the same way.
(If you report the employer, the incidence will not be counted against your future work pass applications, since it wasn't your fault.)
Also, please post the name of the company here, so others are warned not to trust this employer.
Thanks for doing ypur part in preventing work pass crime!