I am travelling from Mumbai to Singapore via Kuala Lampur by AIR ASIA Flights XT-853 and AK 721

According to Timatic, you can transit without a visa.

NOTE: This contradicts George Y's answer, and his source seems ligitimate. I'm not sure which is correct.

I also assume that you're an Indian national, although you didn't explicit

A Timatic search on the Emirates site says:

TWOV (Transit Without Visa): Holders of onward tickets for a max. transit time of 24 hours, arriving at and departing from Kuala Lumpur (KUL).
- Transit without a visa is not possible between Main Terminal and KLIA2.

Holders of a valid visa issued by Australia, China (People's Rep.), Chinese Taipei, Japan, Korea (Rep.), New Zealand or USA to nationals of India residing in India holding confirmed onward tickets for a max. transit time of 120 hours, arriving at and departing from Kuala Lumpur (KUL) on Malaysia Airlines (MH) or Air Asia (AK). When transit time is longer than 8 hours it is permitted to leave the transit area if: - traveling to or returning from the country which issued the visa; and - traveling on a tour/package arranged by a company registered in the country which issued the visa.
- Transit between Main Terminal and KLIA2 is also permitted. When leaving the airport transit area, passports must be valid for at least 6 months from date of arrival.

The first paragraph is applicable to you. It doesn't allow you to leave the ariport or switch between Main Terminal and KLIA2, but both your flights are on KLIA2, so it's OK.

The second paragraph is applicable if you fly Malasiya Airlines (MH) or Air Asia (AK). Your outgoing flight is Indonesia Air Asia X, so it's probably not applicable. If it was, it would allow you to leave the airport.

Assuming your citizenship is Indian, it seems like you're not eligible for TWOV (TWOV means "Transit WithOut Visa"):

Posses a valid onward ticket and carry a Single Entry Visa (SEV) or Multiple Entry Visa (MEV) issued from/and are heading to any one (1) of the seven (7) countries listed below:

Australia
New Zealand
United States of America (USA)
Japan
China
Taiwan
South Korea

*TWOV will not be issued if next country of destination is not listed as above.

You have Taiwanese visa, but since you're not flying to Taiwan it looks like you're not eligible for TWOV.

Interestingly if you were flying the other way, you'd be eligible for Visa on Arrival:

Nationals of eligible countries arriving from Thailand or Singapore with a valid visa from their respective countries

The official government site seems to offer similar opinion although worded it differently:

5. TWOV cannot be offered to passenger sponsored by airlines other than Malaysia Airlines and Air Asia. At present only MAS and Air Asia have agreed and accepted all terms and conditions imposed by the Malaysian Government.