As a Gold I got a suite upgrade for 7 nights at Courtyard Seoul Times Square on mixed award/cash booking.

But I did have to email ahead.

Strategy for upgrade on four night award
 

I've had some great upgrades when staying three nights or less...Macau, Hanoi, KL to name a few.
I'm staying four nights at the CY Taipei. I'm intending to book two separate back-to-back awards for two nights each to increase my chances of being upgraded. Whenever I have back-to-back reservations the check-in clerk never bothers to notice the second one until I mention it to them. In this case, I wouldn't mention it until after already having been assigned the first room.

Can't find anything in the plat t/c about 3 night suite upgrades?

Thought it's subject to availability

This is from the Marriott site, but it does not appear to be in the T&Cs: http://www.marriott.com/hotel-promot...ite-upgrade.mi

Do most hotels follow these guidelines?

cannot speak on Japan as usually use Hyatt/Hilton their but in Korea (Plaza), Malaysia, Singapore and Thailand nearly 100% without asking (and will try it out in VN this coming week)

IME, all but Singapore Orchard Rd FS and the Bangkok CY. The Orchard Rd FS gave me a room with dirty stained carpet. Giant stains that looked like someone dropped a diaper were all over the room. I took pictures and posted them at the time. This was on a one night stay, so it was within the three nights mentioned. At the Bangkok CY, I've had three or four stays under three nights and never gotten an UG, even to a corner or larger room.

Hotels where I have gotten UGs on many occasions: Bangkok Soi 57, Marquis, Ren, JW (but only to CL Level), Shanghai JW, KL Ren. Only one stay but got an UG: KL Majestic, Bali Sheraton Kuta Beach, Pattaya FS Resort (no longer a Marriott).

I got suite upgrades this week at the Renaissance Hong Kong (studio suite) and the Marriott Guangzhou Tianhe (1 bedroom). I have frequently gotten upgrades at the Ren, not so often at the GZ property.

My first stay as a gold member with HKIA skycity Marriott was upgraded to a suite after asking through apps

I was upgraded to a suite at the JW Singapore 2 weeks back, with a super early 8am check-in. Staff and service was incredible there.

From Oct 21-Nov2, as gold.
1 night JW Marriott Hong Kong - Nothing.
5 nights Marriott Shenzen Nanshan - Nothing.
2 nights JW Marriott Hong Kong - Nothing. Executive level mountain (booked base)
3 nights Marriott Shenzhen Nanshan - Executive Suite
1 night Courtyard Hong Kong - TBD.

Majestic Hotel, Kuala Lumpur, Malaysia
1-night, upgraded into colonial suite in old wing

Renaissance, Kuala Lumpur, Malaysia
7 nights, upgraded into Renaissance suite in west wing

J.W. Marriott, Kuala Lumpur, Malaysia
5 Nights, executive suite on top floor

Upgraded to suite every single time so far (~7 stays if memory serves) at Marquis in Bangkok, stays ranging from 2 to 11 nights.

The hotel is massive and I think they have a healthy complement of suites, which probably helps.

As does the Soi 57 FS. The Ren, JW and CY do not have as many suites so the UG are fewer and farther between.

In the Manila Marriott I got upgrades 3/7. In the Suhkumvit Marriott in Bangkok, we got an upgrade 3 days into our 9 day stay. In Beijing, I received a suite at the Renaissance for 5 days in 2012, but not at the JW last july for 5 days.