Good question! I should write the history down as a record before everyone forgets about it. Someone please correct me if I am wrong.
We had 5 AM Medium Wave stations in the past broadcasting from the then Telecoms Transmitter Site in Boon Lay. The site is now either an HDB estate, an MRT station, a shopping centre, or all three.
English Service: 630 kHz, 50 kW Mandarin Service: 990 kHz, 50 kW Malay Service: 675 kHz, 50 kW Tamil / Chinese Dialect Service: 1368 kHz, 50 kW Regional Service High Power Evening Parallel Relay 6 pm - 12mn: 792 kHz, 250?kW
These broadcasts were also paralleled on Shortwave broadcasting from the same Boon Lay site, but later on from Kranji (next door to BBC's Far Eastern Relay) as Radio S'pore International.
English: 5052, 11940, then as RSI English: 6080, 6150, then 6080 and 6155 Chinese: 6000, 9635 Bahasa Malay: 6135, 7250 Tamil: 7170
The AM stations were there first to be decommisioned. I don't have the dates but I think it was around the turn of the century.
The next to go were the SW stations when The Authority believed that the majority of our target audience had the internet. The other reason is that the land on which the transmitters were sitting on could be put to better use. The Boon Lay Site was also home to the Aeronatical HF and Marine MF/HF transmitters.
In the 1960-1970s, we had 5 FM stations: 88.9 BBC World Service from Tanglin (later from Bukit Batok) 90.5 English 92.4 Classical Channel (in Stereo 6 pm to 12 mn - Big Deal then!) 94.2 Bahasa Malay 95.8 Mandarin 96.8 Tamil
With only 5 stations then, you could easily pick up Thai FM stations on days when Sporadic E propagation was active in the afternoons. And you could also pick up the image channel for Singapore Radar 120.3 MHz on 98.9 MHz from Paya Lebar International Airport if your receiver had the Local Oscillator tracking High.
Sorry for the digression, but back to AM transmitters. The closest we have to AM Broadcasting (technically speaking) now are the Aeronautical Non-Directional Beacons (NDB). On the Mainland, currently, we have only 3 beacons:
There used to be more but are now decommisioned: Changi (CH) 342 kHz Paya Lebar North Locator (NN) 338?kHz Paya Lebar South Locator (SS) 325 kHz St. John / Sinjon (SJ) 265 kHz Bukit Timah (BT) 288 kHz Tengah (TN) 215 kHz Horsburgh (PB) 301.5 kHz [offshore]