But the redemption rates are not great.
Update 16 Oct 19: Alaska Air has removed the ability to book a stopover for intra-Asia itineraries, and also adjusted the zones for Beijing and Shanghai. Read more here.
After a very long time, Alaska Air has finally added Singapore Airlines as an award partner.
Since two years ago, you could credit your Singapore Airlines flying with Alaska Air Mileage Plan, which gave excellent mileage especially if you are flying premium classes. For instance, if you are flying first class on a revenue ticket, you will earn 350% of the actual miles flown. Wow.

Award charts are not great
Alaska Air has finally published some semblance of an award chart for Singapore Airlines flights, but they are rather disappointing.
[UPDATE] Following the update of the award chart, China is now classified under North Asia, resulting in a bump in the miles required. Hong Kong and Taiwan remains under “Southeast Asia”, requiring less miles.
Also, Alaska Air no longer allow for a stopover for intra-Asia travel, which means you effectively can’t get two tickets in one anymore.

Note that Alaska Air has peculiarly categorised China, including Hong Kong and Taiwan as “Southeast Asia”, so that means that you can book a one-way ticket from Beijing to Sydney for 65,000 miles in Business.
The usual rule of one stopover is possible on a one-way ticket, so if you don’t want to do the USD100 stopover trick with your Krisflyer miles, you can also explore using Alaska Air Mileage Plan miles.
Alaska Air Mileage Plan miles are also particularly useful for backtracking (e.g. Tokyo-Singapore-Bangkok), since you can’t do that on SQ.
How does it compare to Krisflyer own redemption rates?
To sum it up: Krisflyer comes up cheaper.
The only bright spot in the entire chart is for itineraries involving China, Hong Kong and Taiwan. For some unknown reason, the three regions are considered as “Southeast Asia” by Alaska Air (now, no jokes about Americans not knowing where Singapore is), but this is clearly working in member’s advantage.
See below for the comparison chart (updated 17 Oct 19):

[UPDATE] Alaska Air has revised some of the mileage required for award tickets over the last couple of days, including the Southeast Asia-China and Southeast Asia-India mileage, making the chart very unattractive in comparison to SQ’s own Krisflyer. Having said that, there are still rare cases where it makes sense to use Alaska Air Mileage Plan to redeem for SQ tickets, such as when you are travelling between the Middle East or US to Asia, or vice versa.
Also, as Alaska Air allows you to build in one free stopover in any one-way award, you can literally book two segments in a single award ticket, such as Beijing-Singapore and then Singapore-Hong Kong in business class for 25,000 miles. You will not be able to build such an itinerary using Krisflyer miles, so this is where Alaska Air comes up better.
Final thoughts
For Singapore based members, this new development on Alaska Air Mileage Plan is not overly impressive, particularly if you have a healthy stash of Krisflyer miles. With Krisflyer no longer adding surcharges to its award tickets, they may still make sense for simple, straightforward one-way redemptions.
If you compare most city pairs, Krisflyer still comes up a little cheaper in terms of miles. Given that there’s no easy way to earn Alaska miles, it might make a lot more sense to save them for your Japan getaways on Japan Airlines.
Addendum (17 Oct 19): Given the latest developments on Alaska Air pulling off the complimentary stopover for one-way itineraries within Asia, this has made Alaska Air Mileage Plan significantly less attractive as a programme. However, even with the ‘devaluation’ (I personally don’t see it as a true devaluation given that it was a loophole that was exploited to begin with), some redemptions are still good value: a one-way business class award ticket from Singapore to Tokyo for only 25,000 miles remain very competitive, compared to the 49,000 required by Krisflyer. The only caveat is how you accrue those miles: Alaska Air remains a rare partner for local banks, so your only way to get the miles is by actually flying.