I am an Indian and have multiple entry pass valid for the next 2 years. Suppose if I enter Singapore on a tourist visa on 23rd December and stayed for the next 30 days, i.e. till 23rd January. Now I leave or exit from Singapore on 22nd January to travel either to Malaysia or Indonesia for a 2-3 days trip, can I return to Singapore and then again stay for 30 days?
In theory, you are allowed to do that. However, there is a high chance of you being questioned while entering Singapore again within a week after exhausting your 30-day stay period.
You will have to justify your purpose of visit and the onus will be on you to convince the officer that you are going to return to your home country. Do book your return tickets and also present the concrete itinerary. The officer will have to be certain that you are not going to abuse your visa.