Update
After I've completed my outbound, I've given another try on the website, it got accepted.
The website said that I'd hear back in 3 business days, I received an automated reply immediately. I sent it on 25, and I've received the confirmation last night, albeit in Chinese.
昆明如家睿柏云酒店（原云之行七花酒店）after googling, it seems like Home Inn near the airport.
客人到达机场出站口请拨打接机专线电话 I hope MU counter will be open after I'll arrive after midnight to help me call a shuttle, or wish me luck!
one concern is that as my arrival time is shortly after midnight, so I've enter the actual date. Then the confirmation showed the check in date is the actual date, but check out is on the following day. In conventional sense, the check in normally doesn't start till afternoon of that date, so I'll reply to MU that hotel understands that I'll be arriving after midnight.
anyway, now I have a hotel confirmation to show to the immigration officer, so it's a one step forward.
Ps: I check MU site regularly, because I'm really close to 24hrs in China to barely qualify for twov. A small schedule change may screw this up. I almost had a heart attack when I saw an MU flight leaving bkk 7:50 arriving kmg 11:20! My flight is actually 19:50, arriving kmg 00:05, so I'm still ok, but if it changes to 23:20 arrival, I'll be screwed. Funny MU has flights leaving bkk at 7:50 AND 19:50! Does anybody know why my flight is blocked at 3h15m, while other MU flights are blocked at 2h30m? I find it bizzar as airports should be less congested in the night.