Visa Extention

Your mom might get a 89 days extension the first time.
But if she visits again after a short period (less than the time she spend inside Singapore before), even getting 30 days on arrival is uncertain - and any extension even more so.
The Singapore authorities do NOT like any attempt to circumvent the rules like this and it will NOT be possible to keep your mom here or any longer duration without a proper residence visa.
Please spare the old lady the stress of being denied entry at Changi and being sent back home on the next available flight!

The minimum salary requirement to bring your mom on LTVP is S$12000/month.

Okay, Thank you Beppi for giving me very useful advice.
May I know as per the Authority how many days she needs to stay in her home country before coming back again?

There is no official rule for this - it all depends on the impression of the immigration officer she faces at the counter and his/her superiors when she is asked or questioning in a side room (which is almost certain to happen on her second or third visit).
My personal opinion, which I already wrote above, is that she should stay out of the country for at least as long as she was inside before. But this will also not work any more for the third or subsequent looong visit.
Again: DO NOT TRY TO CIRCUMVENT THE RULES AND ATTEMPT TO BRING HER HERE ON RESIDENCY-LIKE CIRCUMSTANCES WITHOUR PROPER RESIDENCY VISA!!!

You had asked the same in PM, and I said it clearly that avoid this. There is no way your mom could stay for Long period and as Beppi said, any denial at the immigration checkpoint will create trouble to her.

Yes, you need basic salary per annum at least S$144k to bring your parents under LTVP. So, take decision wisely. Good luck

Please note that sending such questions to others as PM is considered SPAM on this forum (especially if these others don't know you and did not give their consent to be contacted).
It is also annoying, wastes the time of the site's volunteers and disables ohers from reading, contributing to and benefitting from the discussion.
Please learn some netiquette and don't do it again!

@beppi and  @Surya2k, Really Thank you for giving me important information. It was helpful.
Also, I would like to know what if Me and My wife both earn a total salary of 12k per month. so in that case, will it be possible to apply for LTVP jointly? (Assuming me and my wife both holding EP pass)

Answer is NO. Either of you must earn $144k in order to fall into this bracket.

Okay, Thanks Surya, Great to know.

You can find more details in below MoM website, you may visit their FAQ section to clarify your further questions. Good luck

https://www.mom.gov.sg/passes-and-permi … ligibility